Androgen action via testicular arteriole smooth muscle cells is important for Leydig cell function, vasomotion and testicular fluid dynamics

Regulation of blood flow through the testicular microvasculature by vasomotion is thought to be important for normal testis function as it regulates interstitial fluid (IF) dynamics which is an important intra-testicular transport medium. Androgens control vasomotion, but how they exert these effects remains unclear. One possibility is by signalling via androgen receptors (AR) expressed in testicular arteriole smooth muscle cells. To investigate this and determine the overall importance of this mechanism in testis function, we generated a blood vessel smooth muscle cell-specific AR knockout mouse (SMARKO). Gross reproductive development was normal in SMARKO mice but testis weight was reduced in adulthood compared to control littermates; this reduction was not due to any changes in germ cell volume or to deficits in testosterone, LH or FSH concentrations and did not cause infertility. However, seminiferous tubule lumen volume was reduced in adult SMARKO males while interstitial volume was increased, perhaps indicating altered fluid dynamics; this was associated with compensated Leydig cell failure. Vasomotion was impaired in adult SMARKO males, though overall testis blood flow was normal and there was an increase in the overall blood vessel volume per testis in adult SMARKOs. In conclusion, these results indicate that ablating arteriole smooth muscle AR does not grossly alter spermatogenesis or affect male fertility but does subtly impair Leydig cell function and testicular fluid exchange, possibly by locally regulating microvascular blood flow within the testis.     

A simple technique for collecting blood of testicular origin: application to in vivo studies on testicular steroidogenesis in rats and Macaca fascicularis

A technique for rapidly collecting blood of testicular origin is described, one which can provide sufficient plasma amounts to investigate some steps of testicular steroid biogenesis in vivo in 2 species. In adult male rats, testosterone (T), androstenedione (4A) and 5-androstenediol (5AD) were determined in pampiniform plexus testicular venous blood (PPTV) and peripheral (PV) blood samples before and 2 h after human Chorionic Gonadotropin (hCG). PPTV concentration of 5AD was 0.83 +/- 0.1 ng/ml (mean +/- SEM) with a PPTV/PV ratio of 7.0 +/- 1.0, comparable to a PPTV/PV ratio for 4A of 5.8 +/- 1.8. After hCG, PPTV concentration of 5AD significantly increased to 1.28 +/- 0.15 ng/ml (P less than 0.05). Those data are in favor of a participation of 5-ene pathway to testicular biogenesis of T associated to a 4-ene pathway which is predominant. In adult male Macaca fascicularis, spermatic vein (SV) concentrations of 5AD and 4A were comparable (3.0 +/- 1.2 vs 4.3 +/- 1.0 ng/ml) as well as SV/PV ratios under basal conditions (3.5 +/- 0.9 vs 5.1 +/- 0.1), as well as 48 h after hCG, confirming in vivo that both 5-ene and 4-ene pathways are involved in testicular T biogenesis. Testicular production of estradiol (E2), estrone (E1) and their sulfates E2S and E1S showed a SV/PV ratio significantly higher than 1 (3.4 +/- 0.6; 2.4 +/- 0.1; 1.7 +/- 0.2 and 1.6 +/- 0.2, respectively).     

Experimental varicocele does not affect the blood-testis barrier, epididymal electrolyte concentrations, or testicular blood gas concentrations

It has been previously shown that 30-day experimental left varicocele (ELV) in adult rats produces a bilateral increase in testicular blood flow and temperature, as well as a concomitant decrease in epididymal sperm count and motility. In the present study, adult male rats with induced ELV were subjected to a variety of studies to determine the mechanism by which unilateral ELV causes a bilateral testicular response. The results demonstrate that ELV does not alter the blood-testis barrier (BTB) to 3H-inulin (MW 5000), it being largely excluded from entry into the tubule lumen in both control and ELV animals. Neither left nor right cauda epididymidal temperature was altered by ELV. Intraepididymal Na+ and K+ concentrations in the left caput epididymidis were 81.3 +/- 3.8 mEq/l and 26.3 +/- 1.5 mEq/l, respectively. From the cauda epididymidis, these values were 25.0 +/- 2.2 mEq/l and 46.8 +/- 1.0 mEq/l, respectively. These values were similar on the right side and in the left and right epididymis of ELV animals. Left testis arterial pH was 7.3 +/- 0.1, and PO2 and PCO2 were 116.0 +/- 6.4 mm of mercury and 44.3 +/- 3.2 mm of mercury, respectively. Left testicular venous values were 7.3 +/- 0.1 (pH), and 52.6 +/- 2.2 mm of mercury and 49.9 +/- 2.0 mm of mercury. These values were similar for right control testicles and left and right testicles of ELV animals. These results indicate that the mechanism by which unilateral ELV produces a bilateral change in testicular or epididymal function is not by altering the BTB, epididymal temperature or electrolyte concentrations, or testicular blood gas concentrations.     

Role of UCH-L1/ubiquitin in acute testicular ischemia-reperfusion injury

The most significant complication of testicular torsion is loss of the testis, which may lead to impaired fertility. Molecular mechanisms how spermatogenesis impairs owing to testicular torsion remain unknown. This investigation, by using mouse model of testicular torsion, was undertaken to gain insight into the cellular and molecular mechanism underlying torsion-induced germ cell loss. Male mice were subjected to 2 h ischemia-inducing torsion, and testes were examined at 24, 48, and 72 h after the repair of torsion (reperfusion). Ischemia-reperfusion (IR) of the testes resulted in germ cell, mostly in spermatogonia, apoptosis, which was revealed by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) technique. At 24 h after torsion repair germ cell apoptosis reached peak, then decreased until 72 h repair. Western blots showed that apoptotic proteins (p53, Caspase-3 and -9) gradually were upregulated at 48 h reperfusion, however, anti-apoptotic proteins (Bcl-2 and BDNF) were downregulated in the relevant IR treatment. IR injury induced CHOP protein appearance with maximum expression at 24 h of reperfusion. Furthermore, the germ cell apoptosis triggered downregulation of ubiquitin carboxyl-terminal hydrolase-L1 (UCH-L1) at both mRNA and protein levels. To test further whether ubiquitination was involved in IR stress, both mono- and poly-ubiquitin levels in IR stress condition were examined, which showed that both mono- and poly-ubiquitin expression significantly impaired. These results provide evidences of UCH-L1/ubiquitination signaling to the testis IR injury in vivo.     

Effects of severe reduction in maternal placental blood flow on blood flow distribution in the sheep fetus

To test the hypothesis that fetal lambs are able to maintain oxygen delivery to myocardial, brain and adrenal tissues during reduction in uterine blood flow to 25% of control, we performed experiments on five ewes and their fetuses. A snare occluder was placed around the maternal common hypogastric artery and catheters were placed for measurement of blood pressures, flows, blood gas tensions, pH and oxygen content. After a five day recovery period, control measurements were made. The snare occluder was then closed until the artery was fully occluded. The arterial occlusion caused uteroplacental blood flow to fall to 32 +/- 4% and maternal placental blood flow to fall to 25 +/- 3% of control values. This level of asphyxia was maintained for 19 +/- 3 minutes, when maternal and fetal blood flows were measured again. In response to occlusion, fetal ascending aortic PO2 fell from 21 +/- 2 (SEM) to 13 +/- 2 mmHg (P less than or equal to 0.01), oxygen content from 4.3 +/- 0.3 to 1.4 +/- 0.2 mM (P less than or equal to 0.01) and pH from 7.37 +/- 0.01 to 7.21 +/- 0.05 (P less than or equal to 0.01). PCO2 rose from 48 +/- 1 to 62 +/- 3 mmHg (P less than or equal to 0.01). Fetal arterial blood pressure increased from 51 +/- 3 to 61 +/- 3 mmHg (P less than or equal to 0.001) and heart rate decreased from 172 +/- 10 to 104 +/- 4 beats.min-1 (P less than or equal to 0.01). The heart, brain and adrenals showed vasodilation in response to the asphyxic stimulus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Fetal pulmonary vasodilation and vasoreactivity during metabolic acidaemia

We studied the pulmonary vascular response to progressive metabolic acidaemia and to an abrupt increase in oxygen tension during metabolic acidaemia in 8 chronically-prepared fetal sheep. Left pulmonary artery blood flow was measured by electromagnetic flow transducer. Two and a half hour infusion of NH4Cl into the fetal inferior vena cava caused pH to fall to 6.94 +/- 0.01 from 7.37 +/- 0.01 (P less than 0.001). During this period of progressive metabolic acidaemia, left pulmonary artery blood flow increased from a baseline value of 60 +/- 8 to 105 +/- 14 ml.min-1 (P less than 0.002). Pulmonary artery pressure did not change significantly and calculated pulmonary vascular resistance fell indicating fetal pulmonary vasodilation. PO2 rose significantly (19.8 +/- 0.7 to 24.1 +/- 1.8 torr; P less than 0.03) and oxygen saturation fell (54.6 +/- 2.8% to 38.9 +/- 3.5%; P less than 0.001) confirming a rightward shift of the oxyhaemoglobin dissociation curve. During acidaemia, administration of 100% oxygen to the ewe further increased fetal PO2 to 37.9 +/- 2.3 torr within 10 min (P less than 0.001) and this increase in PO2 was accompanied by an increase in left pulmonary artery blood flow (P less than 0.001), a fall in pulmonary artery pressure (P less than 0.03) and a decrease in pulmonary vascular resistance (P less than 0.001) indicating further vasodilation. The response of the fetal pulmonary circulation to a 2-h period of increased oxygen tension was qualitatively similar in acidaemic and non-acidaemic fetuses. We conclude that the progressive metabolic acidaemia imposed by these experimental conditions increases pulmonary blood flow likely through an increase in fetal PO2 and that metabolic acidaemia does not block the normal vasodilatory response to an increase in oxygen tension.     

Oxygen tension distribution in postcapillary venules in resting skeletal muscle

We tested the hypothesis that blood flow is distributed among capillary networks in resting skeletal muscle in such a manner as to maintain uniform end-capillary PO2. Oxygen tension in venules draining two to five capillaries was obtained by using the phosphorescence decay methodology in rat spinotrapezius muscle. For 64 postcapillary venules among 18 networks in 10 animals, the mean PO2 was 30.1 Torr (range, 9.7-43.5 Torr) with a coefficient of variation (CV; standard deviation/mean) of 0.26. Oxygen levels of postcapillary venules within a single network or single animal, however, displayed a much smaller CV (0.064 and 0.094, respectively). By comparison, the CV of blood flow in 57 postcapillary venules of 17 networks in 9 animals was 1.27 with a mean flow of 0.011 +/- 0.014 nl/s and a range of 3.7 x 10(-4) to 6.5 x 10(-2) nl/s. Blood flow of postcapillary venules within single networks displayed a lower CV (mean, 0.51), whereas that in individual animals was 0.78. Results indicate that among venular networks, heterogeneity of oxygen tension is less than that of blood flow and within venular networks the heterogeneity of oxygen tension is much less than that of blood flow. In addition, postcapillary PO2 was independent of flow among venules in which both were measured. Results of this study may be attributable to three factors: 1) O2 diffusion between adjacent capillaries and venules, 2) structural remodeling in regions of lower PO2, and 3) O2-dependent local control mechanisms.     

VO2/power output relationship and the slow component of oxygen uptake kinetics during cycling at different pedaling rates: relationship to venous lactate accumulation and blood acid-base balance.

In this experiment we studied the effect of different pedalling rates during cycling at a constant power output (PO) 132+/-31 W (mean+/-S.D.), corresponding to 50% VO2 max, on the oxygen uptake and the magnitude of the slow component of VO2 kinetics in humans. The PO corresponded to 50% of VO2 max, established during incremental cycling at a pedalling rate of 70 rev.min(-1). Six healthy men aged 22.2+/-2.0 years with VO2 max 3.89+/-0.92 l.min(-1), performed on separate days constant PO cycling exercise lasting 6 min at pedalling rates 40, 60, 80, 100 and 120 rev.min(-1), in random order. Antecubital blood samples for plasma lactate [La]pl and blood acid-base balance variables were taken at 1 min intervals. Oxygen uptake was determined breath-by-breath. The total net oxygen consumed throughout the 6 min cycling period at pedalling rates of 40, 60, 80, 100 and 120 rev.min(-1) amounted to 7.727+/-1.197, 7.705+/-1.548, 8.679+/-1.262, 9.945+/-1.435 and 13.720+/-1.862 l, respectively for each pedalling rate. The VO2 during the 6 min of cycling only rose slowly by increasing the pedalling rate in the range of 40-100 rev.min(-1). This increase, was 0.142 l per 20 rev.min(-1) on the average. Plasma lactate concentration during the sixth minute of cycling changed little within this range of pedalling rates: the values were 1.83+/-0.70, 1.80+/-0.48, 2.33+/-0.88 and 2.52+/-0.33 mmol.l(-1). The values of [La]pl reached in the 6th minute of cycling were not significantly different from the pre-exercise levels. Blood pH was also not affected by the increase of pedalling rate in the range of 40-100 rev.min(-1). However, an increase of pedalling rate from 100 to 120 rev.min(-1) caused a sudden increase in the VO2 amounting to 0.747 l per 20 rev.min(-1), accompanied by a significant increase in [La]pl from 1.21+/-0.26 mmol.l(-1) in pre-exercise conditions to 5.92+/-2.46 mmol.l(-1) reached in the 6th minute of cycling (P<0.01). This was also accompanied by a significant drop of blood pH, from 7.355+/-0.039 in the pre-exercise period to 7.296+/-0.060 in the 6th minute of cycling (P < 0.01). The mechanical efficiency calculated on the basis of the net VO2 reached between the 4th and the 6th minute of cycling amounted to 26.6+/-2.7, 26.4+/-2.0, 23.4+/-3.4, 20.3+/-2.6 and 14.7+/-2.2%, respectively for pedalling rates of 40, 60, 80, 100 and 120 rev.min(-1). No significant increase in the VO2 from the 3rd to the 6th min (representing the magnitude of the slow component of VO2 kinetics) was observed at any of the pedalling rates (-0.022+/-0.056, -0.009+/-0.029, 0.012+/-0.073, 0.030+/-0.081 and 0.122+/-0.176 l.min(-1) for pedalling rates of 40, 60, 80, 100 and 120 rev.min(-1), respectively). Thus a significant increase in [La]pl and a decrease in blood pH do not play a major role in the mechanism(s) responsible for the slow component of VO2 kinetics in humans.     

Resveratrol reduction of infarct size in Long-Evans rats subjected to focal cerebral ischemia

Although vasomotion has been considered a feature of the microvascular bed under physiological conditions, it has also been observed following hypotension in several tissues. In this work, 158 mesenteric microvessels of 36 rats were investigated quantitatively in normovolemic and hemorrhaged animals, focussing on diameter changes, particularly vasomotion incidence and characteristics. The femoral arteries of Wistar rats (body weight BW = 188 +/- 23 g, mean +/- SD) anesthetized with pentobarbital were cannulated for arterial pressure (AP) monitoring and blood withdrawal. The protocol consisted of 15 min control and 30 min of hemorrhagic hypotension (AP = 52 +/- 5 mmHg, hemorrhaged vol. = 17 +/- 4 ml/kg BW). During control normovolemic conditions, analysis of mesenteric microcirculation using intravital videomicroscopy revealed neither arteriolar nor venular vasomotion. During hemorrhagic hypotension (HH) microvascular blood flow reduced to 25% of control. While venules did not show diameter changes during HH, arterioles contracted to 85 +/- 20% of control and arteriolar vasomotion appeared in 42% of the animals and 27% of the arterioles. The amplitude of arteriolar diameter change during HH relative to mean diameter and to control diameter averaged 65 +/- 24% (range: 32-129%) and 41 +/- 10% (range: 25-62%), respectively. Vasomotion analysis showed two major frequency components: 1.7 +/- 0.8 and 7.0 +/- 5.2 cycles/min. Arterioles showing vasomotion had a mean control diameter larger than the remaining arterioles and showed the largest constriction during HH. We conclude that hemorrhagic hypotension does not change venular diameter but induces arteriolar constriction and vasomotion in rat mesentery. This activity is expressed as slow waves with high amplitude and fast waves with low amplitude, and is dependent on vessel size.     

Oxygen-sensitive stages of the cell cycle of human diploid cells

We had established that growth of human diploid WI-38 cells is reversibly inhibited by elevated partial pressures of oxygen (PO2) and we were interested in determining where in the cell cycle growth was delayed. A technique combining cytospectrophotometry and autoradiography was used to determine cell cycle parameters. Confluent cells that were subcultivated and exposed to a PO2 of 365 +/- 8 mm Hg were delayed primarily after DNA synthesis but before metaphase. At a PO2 of 590 +/- 35 mm Hg, most cells did not initiate DNA synthesis, and the few that did, failed to complete the process. When exponentially growing cells that had already begun DNA synthesis were exposed to a PO2 of 590 p 35 mm Hg, they accumulated after completing DNA synthesis but before initiating mitosis. The rate at which (3H)thymidine was incorporated into DNA was inversely correlated with oxygen tension (PO2 of 135--590 mm Hg). These results suggest that the process most sensitive to oxygen causes cells to be delayed after DNA synthesis but before metaphase. Slightly higher PO2's were needed to inhibit the initiation of DNA synthesis. Further, the rate of DNA synthesis is decreased by elevated oxygen tensions.     

Arginine vasopressin reduces intestinal oxygen supply and mucosal tissue oxygen tension

We investigated intestinal oxygen supply and mucosal tissue PO2 during administration of increasing dosages of continuously infused arginine vasopressin (AVP) in an autoperfused, innervated jejunal segments in anesthetized pigs. Mucosal tissue PO2 was measured by employing two Clark-type surface oxygen electrodes. Oxygen saturation of jejunal microvascular hemoglobin was determined by tissue reflectance spectrophotometry. Microvascular blood flow was assessed by laser-Doppler velocimetry. Systemic hemodynamic variables, mesenteric venous and systemic acid-base and blood gas variables, and lactate measurements were recorded. Measurements were performed at baseline and at 20-min intervals during incremental AVP infusion (n = 8; 0.007, 0.014, 0.029, 0.057, 0.114, and 0.229 IU.kg(-1).h(-1), respectively) or infusion of saline (n=8). AVP infusion led to a significant (P < .05), dose-dependent decrease in cardiac index (from 121 +/- 31 to 77 +/- 27 ml.kg(-1).min(-1) at 0.229 IU.kg(-1).h(-1)) and systemic oxygen delivery (from 14 +/- 3 to 9 +/- 3 ml.kg(-1).min(-1) at 0.229 IU.kg(-1).h(-1)) concomitant with an increase in systemic oxygen extraction ratio (from 31 +/- 4 to 48 +/- 10%). AVP decreased microvascular blood flow (from 133 +/- 47 to 82 +/- 35 perfusion units at 0.114 IU.kg(-1).h(-1)), mucosal tissue PO2 (from 26 +/- 7 to 7 +/- 2 mmHg at 0.229 IU.kg(-1).h(-1)), and microvascular hemoglobin oxygen saturation (from 51 +/- 9 to 26 +/- 12% at 0.229 IU.kg(-1).h(-1)) without a significant increase in mesenteric venous lactate concentration (2.3 +/- 0.8 vs. 3.4 +/- 0.7 mmol/l). We conclude that continuously infused AVP decreases intestinal oxygen supply and mucosal tissue PO2 due to a reduction in microvascular blood flow and due to the special vascular supply in the jejunal mucosa in a dose-dependent manner in pigs.     

Is postexercise hypotension related to excess postexercise oxygen consumption through changes in leg blood flow?

After a single bout of aerobic exercise, oxygen consumption remains elevated above preexercise levels [excess postexercise oxygen consumption (EPOC)]. Similarly, skeletal muscle blood flow remains elevated for an extended period of time. This results in a postexercise hypotension. The purpose of this study was to explore the possibility of a causal link between EPOC, postexercise hypotension, and postexercise elevations in skeletal muscle blood flow by comparing the magnitude and duration of these postexercise phenomena. Sixteen healthy, normotensive, moderately active subjects (7 men and 9 woman, age 20-31 yr) were studied before and through 135 min after a 60-min bout of upright cycling at 60% of peak oxygen consumption. Resting and recovery VO2 were measured with a custom-built dilution hood and mass spectrometer-based metabolic system. Mean arterial pressure was measured via an automated blood pressure cuff, and femoral blood flow was measured using ultrasound. During the first hour postexercise, VO2 was increased by 11 +/- 2%, leg blood flow was increased by 51 +/- 18%, leg vascular conductance was increased by 56 +/- 19%, and mean arterial pressure was decreased by 2.2 +/- 1.0 mmHg (all P <0.05 vs. preexercise). At the end of the protocol, VO2 remained elevated by 4 +/- 2% (P <0.05), whereas leg blood flow, leg vascular conductance, and mean arterial pressure returned to preexercise levels (all P >0.7 vs. preexercise). Taken together, these data demonstrate that EPOC and the elevations in skeletal muscle blood flow underlying postexercise hypotension do not share a common time course. This suggests that there is no causal link between these two postexercise phenomena.     

Ischemic exercise and the muscle metaboreflex.

In exercising muscle, interstitial metabolites accumulate and stimulate muscle afferents. This evokes the muscle metaboreflex and raises arterial blood pressure (BP). In this report, we examined the effects of tension generation on muscle metabolites and BP during ischemic forearm exercise in humans. Heart rate (HR), BP, P(i), H(2)PO(4)(-), and pH ((31)P-NMR spectroscopy) data were collected in 10 normal healthy men (age 23 +/- 1 yr) during rhythmic handgrip exercise. After baseline measurements, the subjects performed rhythmic handgrip for 2 min. At 2 min, a 250-mmHg occlusion cuff was inflated, and ischemic handgrip exercise was continued until near fatigue (Borg 19). Measurements were continued for an additional 30 s of ischemia. This protocol was performed at 15, 30, 45, and 60% of the subjects' maximum voluntary contraction (MVC) in random order. As tension increased, the time to fatigue decreased. In addition, mean arterial pressure and HR were higher at 60% MVC than at any of the other lower tensions. The NMR data showed significantly greater increases in H(2)PO(4)(-), P(i), and H(+) at 60% than at 15 and 30% MVC. Therefore, despite the subjects working to the same perceived effort level, a greater reflex response (represented by BP and HR data) was elicited at 60% MVC than at any of the other ischemic tensions. These data are consistent with the hypothesis that, as tension increases, factors aside from insufficient blood flow contribute to the work effect on muscle metabolites and the magnitude of the reflex response.     

Functional arterio-venous anastomoses between the testicular artery and the pampiniform plexus in the spermatic cord of rams

Blood flow to the testis, haemoglobin oxygen saturation and testosterone concentration in arterial and venous testicular blood vessels were studied in Texel rams in the breeding and non-breeding season. Blood flow in the proximal and distal testicular artery was measured electromagnetically. The mean flow in the proximal testicular artery was 18.5 ml/min and in the distal testicular artery 7.5 ml/min, and there was no detectable seasonal influence. Haemoglobin oxygen saturation and testosterone concentration were measured in the saphenous artery and vein, the distal testicular artery and vein, and in the proximal testicular vein. The haemoglobin oxygen saturation in the proximal testicular vein was significantly higher than in the distal testicular vein in both seasons. The mean testosterone concentration was significantly lower in the proximal testicular vein than in the distal testicular vein in both seasons. Based on haemoglobin oxygen saturation and testosterone data, it was calculated that between 28 and 46% of the testicular arterial blood was bypassing the testis and was directly flowing through arterio-venous anastomoses towards the pampiniform plexus in the spermatic cord of conscious rams. In anaesthetized rams 55 and 64% of the blood was flowing directly from the testicular artery to the pampiniform plexus based on blood flow data. Transfer of testosterone and oxygen by passive diffusion from the testicular artery to the pampiniform plexus and vice versa in the spermatic cord was not detected.     

An in-vivo method for estimating inhibin production by adult rat testes

The concentrations of inhibin in samples of rat testicular venous and arterial blood and interstitial fluid were measured by an in-vitro bioassay using pituitary cells in culture in which the standard was an ovine testicular lymph preparation (assigned potency 1 unit/mg). Inhibin levels were undetectable (less than 2 U/ml) in both blood samples but reached a mean concentration of 120 +/- 7 U/ml in testicular interstitial fluid. After unilateral efferent duct ligation the rate of inhibin accumulation in seminiferous tubules was determined by the difference in the inhibin content of the ligated and unligated testes. Additionally, the rate of seminiferous tubule fluid production was obtained from the difference in weight between the ligated and non-ligated testes. In the 24 h after efferent duct ligation there were linear increases in inhibin (18.5 +/- 1.0 U/h) and in seminiferous tubule fluid production (26 +/- 1 microliter/h), but there were no changes in serum FSH and LH levels. Experimental induction of bilateral cryptorchidism led to a decrease in the inhibin content of the testis after 10 days. The rate of inhibin accumulation after efferent duct ligation declined more rapidly than the inhibin content, being significantly depressed in cryptorchid testes after 3 days, suggesting that this measurement is a more sensitive index of inhibin production than the determination of testicular inhibin content.     

Role of nitric oxide in capillary perfusion and oxygen delivery regulation during systemic hypoxia

The role of nitric oxide (NO) and reactive oxygen species (ROS) in regulating capillary perfusion was studied in the hamster cheek pouch model during normoxia and after 20 min of exposure to 10% O2-90% N2. We measured PO2 by using phosphorescence quenching microscopy and ROS production in systemic blood. Identical experiments were performed after treatment with the NO synthase inhibitor NG-monomethyl-L-arginine (L-NMMA) and after the reinfusion of the NO donor 2,2'-(hydroxynitrosohydrazono)bis-etanamine (DETA/NO) after treatment with L-NMMA. Hypoxia caused a significant decrease in the systemic PO2. During normoxia, arteriolar intravascular PO2 decreased progressively from 47.0 +/- 3.5 mmHg in the larger arterioles to 28.0 +/- 2.5 mmHg in the terminal arterioles; conversely, intravascular PO2 was 7-14 mmHg and approximately uniform in all arterioles. Tissue PO2 was 85% of baseline. Hypoxia significantly dilated arterioles, reduced blood flow, and increased capillary perfusion (15%) and ROS (72%) relative to baseline. Administration of L-NMMA during hypoxia further reduced capillary perfusion to 47% of baseline and increased ROS to 34% of baseline, both changes being significant. Tissue PO2 was reduced by 33% versus the hypoxic group. Administration of DETA/NO after L-NMMA caused vasodilation, normalized ROS, and increased capillary perfusion and tissue PO2. These results indicate that during normoxia, oxygen is supplied to the tissue mostly by the arterioles, whereas in hypoxia, oxygen is supplied to tissue by capillaries by a NO concentration-dependent mechanism that controls capillary perfusion and tissue PO2, involving capillary endothelial cell responses to the decrease in lipid peroxide formation controlled by NO availability during low PO2 conditions.     

Protective effect of L-carnitine on testicular ischaemia-reperfusion injury in rats

Testicular torsion is a urological emergency referred to as 'acute scrotum', because inappropriate treatment can lead to male subfertility and infertility. A possible cause of testicular damage is the ischaemia-reperfusion (I/R) injury attributed to oxygen free radicals. L-carnitine, a vitamin-like antioxidant, plays a pivotal role in the maturation of spermatozoa within the reproductive tract. The aim of the present paper was to determine the protective effect of L-carnitine on testicular I/R-induced injury. Thirty-two male rats were divided into 4 groups (n = 8). Testicular torsion was created by rotating the right testis 720 degrees in a clockwise direction. Group 1: sham-operated control; group 2: ischaemia; group 3: I/R; group 4: ischaemia-L-carnitine treatment-reperfusion group. L-carnitine (500 mg kg(-1), intraperitoneally) was administered before 30 min of detorsion in Group 4. After torsion (5 h) and detorsion (5 h), bilateral orchidectomy was performed. The malondialdehyde (MDA) level was evaluated in testes. Histopathologically, Johnsen's spermatogenesis criteria and mean seminiferous tubule diameter (MSTD) measurements were used. Testicular MDA levels were higher in the torsion group compared to the sham-control group (p < 0.05). Detorsion (reperfusion) caused a further increase in MDA levels (p < 0.05). Pretreatment with L-carnitine prevented a further increase in MDA levels (p < 0.05). Histologically, torsion caused some separation among germinal cells in the seminiferous tubules, which became much more prominent in the I/R group but was attenuated with L-carnitine pretreatment. In conclusion, L-carnitine pretreatment may have a protective effect in experimental testicular torsion-detorsion model in rats by its well-known antioxidant potential.     

Regional differences in blood flow and oxygen consumption in resting muscle and their relationship during recovery from exhaustive exercise.

This investigation evaluated regional differences in blood flow and oxygen consumption and their relationship in exercised muscle during recovery from exhaustive exercise. Five healthy men performed exhaustive one-legged cycling exercise. Positron emission tomography was used to measure blood flow, oxygen uptake, and oxygen extraction in the quadriceps femoris muscle before and after exercise. Regions of interest included five areas of the muscle (two proximal, one central, and two distal), which were evenly spaced across the muscle. Before exercise, blood flow and oxygen consumption decreased significantly (P < 0.05) in the direction from the proximal to the distal portions; blood flow declined from 2.0 +/- 0.5 to 1.4 +/- 0.3 ml x 100 g-1 x min-1, and oxygen consumption decreased from 0.21 +/- 0.04 to 0.17 +/- 0.02 ml.100 g-1x min-1. In contrast, these gradients in blood flow and oxygen consumption diminished during recovery after exercise. Consequently, there was a positive relationship between changes in blood flow and oxygen consumption in an exercised muscle during recovery after exercise (r = 0.963, P < 0.01). These changes became larger in the direction from proximal to distal portions: blood flow increased from 2.9 +/- 0.7 to 3.9 +/- 0.8 and oxygen consumption from 1.4 +/- 0.1 to 1.8 +/- 0.4 times resting values. These results suggest that hemodynamic variables are heterogeneous within a muscle both at rest and during recovery from exercise and that there is a systematic difference in these variables in the direction from proximal to distal regions within the quadriceps femoris muscle.     

Increased flow of testicular blood plasma during local heating of the testes of rams.

After removal of the scrotal skin, one testis of each of 12 adult anaesthetized rams was kept at 33 degrees C for 60 min, then heated either to 36 degrees C for 60 min and then to 39 degrees C for 60 min, or to 36 degrees C for 120 min and then returned to 33 degrees C for 100 min, while the other testis was maintained at 33 degrees C. Flow of testicular blood plasma was measured every 10 min using the technique of dilution of sodium p-aminohippurate. When the temperature of the testis was raised to 36 degrees C, flow of blood plasma gradually increased and reached a higher than normal rate at the end of the first hour, without any further increase during the second hour. The increase in mean flow rate was 25.8 +/- 3.4% (mean +/- SEM) during the second hour at 36 degrees C, and 77.1 +/- 12.8% during the hour at 39 degrees C, compared with the respective values at 33 degrees C. No significant changes were seen in testicular lymph flow determined by collection for 10 min in four rams at 36 degrees C (60 min) and then at 39 degrees C (60 min). These results are different from those from earlier studies in which total blood flow was unchanged when the scrotum and testes were heated. The difference could be related either to lack of heating of the scrotum or to the lower temperatures used in the present study.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of reduced uterine blood flow on fetal and maternal cortisol

We have measured the changes in fetal and maternal plasma concentrations of cortisol in relation to blood gases and percent oxygen saturation during 2- and 4-h episodes of reversibly reduced uterine blood flow in sheep between 120 days gestation and term. During that period of reduced uterine blood flow there was a significant decrease in fetal arterial percent oxygen saturation (SaO2), PO2 and pH. Fetal SaO2 decreased from 59.5 +/- 3.2% to 31.8% +/- 2.8% by 15 min, 32.9 +/- 2.9% by 60 min, and 33.5 +/- 2.9% by 120 min. Fetal PO2 decreased from 3.2 +/- 0.1 KPa to 2.0 +/- 0.2 KPa by 15 min, 2.2 +/- 0.2 KPa by 60 min and 2.3 +/- 0.1 KPa by 120 min. Fetal pH decreased from 7.36 +/- 0.01 to 7.30 +/- 0.03 by 15 min, 7.27 +/- 0.02 by 60 min and 7.25 +/- 0.03 by 120 min. During the period of reduced uterine blood flow, fetal plasma concentrations of cortisol increased from 37.1 +/- 10.8 nmol/l to 53.3 +/- 9.2 nmol/l by 15 min, 49.2 +/- 11.4 nmol/l by 60 min and 43.3 +/- 9.0 nmol/l by 120 min. The greatest percentage increase in fetal plasma concentrations of cortisol occurred in fetuses of 126-139 days gestation. There was no significant change in maternal blood gases, SaO2 or plasma concentrations of cortisol. These experiments demonstrate that there is a significant increase in fetal plasma concentrations of cortisol in response to reductions in uterine blood flow from as early as 120 days gestation.