Direct positive chronotropic action by angiotensin II in the isolated mouse atrium

We observed the direct positive chronotropic effect of angiotensin II in mouse atria and characterized its pharmacological property. C57BL/6J mice were anesthetized with pentobarbital and hearts were quickly excised. Atrial preparations including right and left atrium were isolated and suspended in the organ bath filled with Krebs-Henseleit solution gassed with 95% O2 and 5% CO2. Angiotensin II at concentrations of 10(-10) to 10(-6) M caused concentration-dependent increase in heart rate, and the maximal response was about 13% of that by isoproterenol. The effect was blocked by the selective AT1-receptor antagonist, losartan at concentrations of 10(-6) M, but not by the selective beta-blocker, nadolol at concentration of 10(-5) M. Furthermore, angiotensin I also caused concentration-dependent increase in heart rate, and the effect was blocked by angiotensin converting enzyme (ACE) inhibitor, captopril at concentrations of 10(-6) M. These results suggested that angiotensin I is converted to angiotensin II via ACE system in mice atria, and regulate heart rate through AT1-receptor stimulation, not by beta-adrenergic receptor.     

Changes in mouse submaxillary glands after injection of isoproterenol in intact and depancreatized animals

The changes in the relative weight, cell area and ultrastructure of the submaxillary glands (SMG) of CBA/C57BL mice and those in the content of immunoreactive insulin-like protein (IRILP) occurring in the organ were studied. The changes were examined on day 6 after isoproterenol (ISP) injection (23 mg/100 g bw) to healthy animals (group I), on day 13 after pancreatectomy and on day 6 after injection of the indicated dose of ISP (group II), and on day 13 after pancreatectomy without ISP injection (group III). Intact animals served as control. In all the three experimental groups, the ratio between the SMG weight and the total weight of animals showed a tendency towards increase. The highest increase was recorded in group II, where the weight of the SMG was 46.1% higher than the control value. In groups II and III, the area of acinar cells increased by 49.1 and 12.5%, respectively. The area of salivary tube granular ducts decreased by 12.6% in group II and slightly increased (by 4.7% much greater than in group III. Electron microscopy demonstrated that secretory activity of the granular duct cells was enhanced in all the three groups and that secretory extrusion occurred via the apocrine (in group II animals via the holocrine as well) cells. The radioimmunoassay data suggest that IRILP content in the SMG of controls and animals entering groups I-III was 685 +/- 50, 1125 +/- 125, 914 +/- 120 and 302 +/- 66 mu units/g weight, respectively. It is concluded that the synthesis and accumulation of IRILP in the SMG after ISP injection are activated and that the formation and extrusion of IRILP after ISP injection to diabetic animals are overtly activated. Presumably ISP injection to diabetic mice facilitates the stimulation of the compensatory function of the SMG as an IRILP-producing organ.     

Differential ANG II generation in plasma and tissue of mice with decreased expression of the ACE gene

We utilized mice with homozygous disruption of angiotensin-converting enzyme (ACE) (-/-), mice with heterozygous deletion of ACE (+/-), and wild-type mice (+/+) to test the hypothesis that genetic variation in ACE modulates tissue and plasma angiotensin (ANG) II concentrations. With the use of ANG I as substrate, kidney, heart, and lung ACE activity was reduced 80% in -/- mice compared with +/+ mice. However, ANG II concentrations and ANG II-to-ANG I ratios in the kidney, heart, and lung did not differ among genotypes. In contrast, plasma ANG II concentrations in -/- mice were <2 fmol/ml, whereas plasma ANG I concentrations were extremely high (765 fmol/ml). Chymase activity was increased 14-fold in the kidney (P < 0.05) and 1.5-fold in the heart (P < 0.05) of -/- versus +/+ mice but did not differ among genotypes in the lung. ANG II formation from enzymes other than ACE and chymase contributed <2% of total ANG II formation in all genotypes. These data suggest that ACE is essential to ANG II formation in the vascular space, whereas chymase may provide an important mechanism in maintaining steady-state ANG II levels in tissue.     

Role of the area postrema in angiotensin II modulation of baroreflex control of heart rate in conscious mice

This study reports the effects of angiotensin II (ANG II), arginine vasopression (AVP), phenylephrine (PE), and sodium nitroprusside (SNP) on baroreflex control of heart rate in the presence and absence of the area postrema (AP) in conscious mice. In intact, sham-lesioned mice, baroreflex-induced decreases in heart rate due to increases in arterial pressure with intravenous infusions of ANG II were significantly less than those observed with similar increases in arterial pressure with PE (slope: -3.0 +/- 0.9 vs. -8.1 +/- 1.5 beats x min(-1) x mmHg(-1)). Baroreflex-induced decreases in heart rate due to increases in arterial pressure with intravenous infusions of AVP were the same as those observed with PE in sham animals (slope: -5.8 +/- 0.7 vs. -8.1 +/- 1.5 beats x min(-1) x mmHg(-1)). After the AP was lesioned, the slope of baroreflex inhibition of heart rate was the same whether pressure was increased with ANG II, AVP, or PE. The slope of the baroreflex-induced increases in heart rate due to decreases in arterial blood pressure with SNP were the same in sham- and AP-lesioned animals. These results indicate that, similar to other species, in mice the ability of ANG II to acutely reset baroreflex control of heart rate is dependent on an intact AP.     

Blood viscosity and cardiac output in acute experimental anemia.

The significance of blood viscosity alterations during anemia was evaluated in dogs under morphine-chloralose anesthesia. In group I, anemia (mean hematocrit 18.1 +/- 1.3 vol %) was produced by exchange transfusion with clinical dextran (avg mol wt 70,000). In group II, anemia was produced (mean hematocrit 19.9 +/- 0.88 vol %) with 500,000 molecular weight dextran, thus preventing the decrease in blood viscosity in group I. The cardiac output increase in group I (93.4%) with low-viscosity anemia was significantly greater than in group II (43.3%) with unchanged blood viscosity. Group III animals were transfused with a clinical dextran-red cell mixture, and group IV animals received a 500,000 mol wt dextran-red cell mixture. In group III, blood viscosity and cardiac output did not change. In group IV, blood viscosity rose and cardiac output fell significantly. The results suggest that a change in blood viscosity exerts a significant effect upon cardiac output, especially during acute dextran-exchange anemia.     

Effect of increased afterload on right ventricular function in newborn pigs

The effect of a progressive increase in right ventricular (RV) afterload was studied in pigs less than 24 h (group I) and 3-5 days old (group III). RV load was applied to increase mean pulmonary arterial pressure (Ppa) until right to left shunt was observed. Initially, pigs in group I had a significantly lower systemic arterial pressure (Psa = 63 +/- 2 vs. 82 +/- 5 mmHg) and higher Ppa (30 +/- 1 vs. 23 +/- 2 mmHg) even though the RV stroke work (RVSW) was similar (54.3 +/- 10.8 vs. 32.4 +/- 2.1 mmHg/ml) to group II. After a progressive rise in afterload, pigs in group I could maintain a higher RV stroke volume than those in group II (1.3 +/- 0.3 vs. 0.4 +/- 0.1 ml; P less than 0.05). At shunt condition, the RVSW was increased by 21 +/- 14% of the initial value in group I vs. a 32 +/- 8% decrease in group II (P less than 0.05). The ductus arteriosus was constricted and right-to-left shunt was observed in all animals at the foramen ovale level even though Ppa exceeded Psa before the rise in the right atrial pressure in group I. Thus, as RV afterload is increased in the pig, the older animals' right ventricle is progressively less capable of maintaining pulmonary blood flow than animals within 24 h of birth.     

Effect of oxidative stress on the spermatogenic process and hsp70 expressions in mice testes

The effect of oxidative stress on the process of spermatogenesis in terms of hsp70 expression was studied. For creating different oxidative stressed mice, three selenium (Se) levels viz., deficient (group I), adequate (group II) and excess (group III) were fed for 8 weeks in a yeast-based diet. After completion of diet feeding, Se level was significantly decreased in group I and significantly increased in group III, as compared to group II. Glutathione peroxidase (GSH-Px) activity was significantly decreased in both liver and testis in group I animals; however, the activity was comparable in groups II and III. Significant increase in the testis glutathione-S-transferase (GST) activity was observed in group I. No change was seen in group III, when compared to group II. Histological analysis of testis revealed a significant decrease in the germ cell population in group I, as compared to group II, with a predominant effect on spermatid and mature sperm numbers. In group III, displacement of germ cell population was observed. ELISA assays for hsp70 level showed increase in group I as compared to group II, whereas no significant change was observed in group III, as compared to group II. Immunohistochemical analysis revealed intense localization of hsp70 only in spermatid and sperm cells. The expression in groups II and III was homogeneous with slightly increased expression around lumen in group III. The data indicate that excessive oxidative stress in Se deficient group, affects the spermatogenesis process, especially affecting the mature sperm number which in turn leads to infertility.     

Endocrine profiles and embryo quality in the PMSG-PGF2alpha treated cow

Plasma progesterone and LH concentrations around estrus were determined for both PMSG treated (experimental animals) and non-treated (control animals) dairy cows and heifers of the Holstein Friesian and Jersey breeds, and these hormone profiles were related to the embryo quality. Most experimental animals experienced an increase in progesterone concentrations following PMSG treatment and an abrupt decrease to values below 3 nmol/l after PG injection. The mean (+/-SE) intervals from prostaglandin treatment to estrus were 46.9+/-1.8 h and 64.5+/-4.8 h for experimental and control animals, respectively. At the onset of heat the progesterone concentration in experimental animals with optimal embryo quality (group I) was significantly lower (p<0.01) than in experimental animals which yielded unfertilized eggs (group II) (1.2+/-0.1 versus 3.9+/-0.8 nmol/l) and significantly higher than the level in the control group (0.6+/-0.1 nmol/l). Following estrus the progesterone profiles in all 3 groups were studied and the length of the superovulatory cycle was measured to 26.0+/-4.8 days. The preovulatory LH surge occurred sooner after prostaglandin injection in experimental (41 h) than in control animals (65 h). The LH surge in group I occurred within a narrow range and reached a higher average level than group II (24.2+/-2.2 ng/ml and 16.3+/-3.7 ng/ml, respectively). The control group attained an even higher LH surge (31.8+/-8.8 ng/ml) than did the experimental animals. The data presented in this experiment indicate that plasma levels of progesterone and LH in PMSG-PGF(2)alpha treated animals are related to embryo or egg quality.     

Alterations induced by cyclosporine A in myocardial fibers and extracellular matrix in rat

Cyclosporine A (CsA) is the first choice immunosuppressant universally used in allotransplantation. However, it has been demonstrated that this drug produces unwanted side effects in several organs and in particular in the kidney and in the heart. While the cardiac toxicity, due to alteration of myocardial prostanoid has been reported, no data are available about the effects of CsA on myocardial cytoarchitecture. We studied the CsA induced alterations of the myocardial structure and of the extracellular matrix components (ECM). To test the ECM enzymatic chances we studied a family of enzymes (matrix metalloproteinase-MMP), responsible for the degradation of extracellular matrix components. In particular we investigated MMPI, MMP2 and MMP9. The study was carried out on two groups of Wistar rats. The group I animals served as a control and were injected subcutaneously daily with castor oil for 21 days. Group II: animals were subcutaneously injected daily with CsA (dose: 15 mg/Kg in castor oil) for 21 days. The group I animals (control) had normal heart architecture and low levels of MMPI, MMP2 and MMP9. The group II animals showed degenerative changes with myocardial fibrosis, low levels of MMP1 and MMP9 but a clear increase in MMP2. We suggest that the myocardial fibrosis was a consequence of the cardiotoxic effect of CsA determining the alteration of the balance between synthesis and degradation of ECM. The increase in MMP2 suggests that this enzyme could play a protective role during myocardial damage and represent a compensatory mechanism for the excessive accumulation of collagen.     

Cardioprotection by Inula racemosa Hook in experimental model of myocardial ischemic reperfusion injury

To evaluate the cardioprotective potential of Inula racemosa in myocardial ischemic-reperfusion injury, Wistar male albino rats were randomly divided into four groups. The group I and II animals were administered saline orally {(sham, ischemia- reperfusion (I-R) control group)} and animals of group III and group IV received I. racemosa extract (100 mg/kg) for 30 days. On the 30th day, animals of I-R control and I. racemosa treated groups were underwent 45 min of ligation of left anterior descending coronary artery and were thereafter re-perfused for 60 min. In the I-R control group, a significant decrease of mean arterial pressure (MAP), heart rate (HR), contractility, (+)LVdP/dt and relaxation, (-)LVdP/dt and an increase of left ventricular end diastolic pressure (LVEDP) were observed. Subsequent to haemodynamic impairment and left ventricular contractile dysfunction, a significant decline was observed in endogenous myocardial antioxidants; superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and reduced glutathione (GSH). Increased lipid peroxidation characterized by malonaldialdehyde (MDA) formation along with depletion of cardiomyocytes specific enzymes, creatine phosphokinase-MB (CK-MB) isoenzyme and lactate dehydrogenase (LDH) in I-R control group compared to sham group revealed I-R injury of heart. However, treatment with I. racemosa significantly restored the myocardial antioxidant status evidenced by increased SOD, CAT, GPx and GSH and prevented leakage of cardio-specific enzymes; CK-MB and LDH and favorably modulated the altered MAP, HR, (+)LVdP/dt, (-)LVdP/dt and LVEDP as compared to I-R control. Furthermore, I-R induced lipid peroxidation was significantly inhibited by I. racemosa treatment. These beneficial cardioprotective effects translated into significant improvement in cardiac function. In conclusion, our study has demonstrated that the cardioprotective effect of I. racemosa likely resulted to improved antioxidant status, haemodynamic and left ventricular contractile function subsequent to suppression of oxidative stress.     

Prophylactic use of ceftriaxone in combination with F I antigen immunization in studies on uninbred albino mice infected by Yersinia pestis. Antiplague immunity development]

Administration of highly immunogenic (ED50 12.6 mcg/mouse) F I antigen (100 mcg/mouse) to albino mice 5 hours after their contamination approximately with 1000 LD50 of Yersinia pestis 231 provided 99-percent survival of same animals (17-50%) and 2-5-day prolongation of the life-span, that was indicative of the phenomenon analogous to the survival phenomenon observed in infected animals immunized by immunogenic strains of the plague microbe. The experiment on the mice confirmed high efficacy of ceftriaxone (100-percent survival) when used prophylactically for 5 days 5 hours after the contamination by Y. pestis 231 (approximately 1000 LD50) in the dose equivalent to the daily dose for humans. However, no antiplague immunity developed in the survivors: the immunity index (II) of 1.5x10. The use of ceftriaxone according to the same scheme simultaneously with single immunization by F I antigen in a dose of 100 mcg/mouse resulted not only in 100-percent survival of the animals but also in development of expressing antiplague immunity (II 2.2x10(5)). The protection level corresponded to the control with the same live-stock of the animals after a single immunization in the analogous dose of F I antigen (II 3.2x10(4)) and the ceftriaxone use (II 1.0x10(5)), as well as after immunization of the mice by 10(6) microbial cells of Y. pestis EV NIIEG (II 1.2x10(5)). The results of the study are indicative of the prospective use of subsingle vaccines of the new generation based on F I antigen for combined specific and urgent prophylaxis.     

Overexpression of TRPC3 increases apoptosis but not necrosis in response to ischemia-reperfusion in adult mouse cardiomyocytes

An increase in cytosolic Ca2+ via a capacitative calcium entry (CCE)-mediated pathway, attributed to members of the transient receptor potential (TRP) superfamily, TRPC1 and TRPC3, has been reported to play an important role in regulating cardiomyocyte hypertrophy. Increased cytosolic Ca2+ also plays a critical role in mediating cell death in response to ischemia-reperfusion (I/R). Therefore, we tested the hypothesis that overexpression of TRPC3 in cardiomyocytes will increase sensitivity to I/R injury. Adult cardiomyocytes isolated from wild-type (WT) mice and from mice overexpressing TRPC3 in the heart were subjected to 90 min of ischemia and 3 h of reperfusion. After I/R, viability was 51 +/- 1% in WT mice and 42 +/- 5% in transgenic mice (P < 0.05). Apoptosis assessed by annexin V was significantly increased in the TRPC3 group compared with WT (32 +/- 1% vs. 21 +/- 3%; P < 0.05); however, there was no significant difference in necrosis between groups. Treatment of TRPC3 cells with the CCE inhibitor SKF-96365 (0.5 microM) significantly improved cellular viability (54 +/- 4%) and decreased apoptosis (15 +/- 4%); in contrast, the L-type Ca2+ channel inhibitor verapamil (10 microM) had no effect. Calpain-mediated cleavage of alpha-fodrin was increased approximately threefold in the transgenic group following I/R compared with WT (P < 0.05); this was significantly attenuated by SKF-96365. The calpain inhibitor PD-150606 (25 microM) attenuated the increase in both alpha-fodrin cleavage and apoptosis in the TPRC3 group. Increased TRPC3 expression also increased sensitivity to Ca2+ overload stress, but it did not affect the response to TNF-alpha-induced apoptosis. These results suggest that CCE mediated via TRPC may play a role in cardiomyocyte apoptosis following I/R due, at least in part, to increased calpain activation.     

CCR2 mediates the uptake of bone marrow-derived fibroblast precursors in angiotensin II-induced cardiac fibrosis

Angiotensin II plays an important role in the development of cardiac hypertrophy and fibrosis, but the underlying cellular and molecular mechanisms are not completely understood. Recent studies have shown that bone marrow-derived fibroblast precursors are involved in the pathogenesis of cardiac fibrosis. Since bone marrow-derived fibroblast precursors express chemokine receptor, CCR2, we tested the hypothesis that CCR2 mediates the recruitment of fibroblast precursors into the heart, causing angiotensin II-induced cardiac fibrosis. Wild-type and CCR2 knockout mice were infused with angiotensin II at 1,500 ng·kg(-1)·min(-1). Angiotensin II treatment resulted in elevated blood pressure and cardiac hypertrophy that were not significantly different between wild-type and CCR2 knockout mice. Angiotensin II treatment of wild-type mice caused prominent cardiac fibrosis and accumulation of bone marrow-derived fibroblast precursors expressing the hematopoietic markers, CD34 and CD45, and the mesenchymal marker, collagen I. However, angiotensin II-induced cardiac fibrosis and accumulation of bone marrow-derived fibroblast precursors in the heart were abrogated in CCR2 knockout mice. Furthermore, angiotensin II treatment of wild-type mice increased the levels of collagen I, fibronectin, and α-smooth muscle actin in the heart, whereas these changes were not observed in the heart of angiotensin II-treated CCR2 knockout mice. Functional studies revealed that the reduction of cardiac fibrosis led to an impairment of cardiac systolic function and left ventricular dilatation in angiotensin II-treated CCR2 knockout mice. Our data demonstrate that CCR2 plays a pivotal role in the pathogenesis of angiotensin II-induced cardiac fibrosis through regulation of bone marrow-derived fibroblast precursors.     

Reactions of the adrenal cortex and thyroid gland of hypophysectomized rats to hypothermia

Male Wistar rats were hypophysectomized 7 days (group 1) and 4-7 weeks (group II) before exposure to hypothermia (4 degrees C for 1 1/2 h). The hypophysectomized rats from group I were devoid of both the posterior lobe and the adenohypophysis, while the rats from group II had the posterior hypophysis but not the adenohypophysis regenerated. A decreased arginine-vasopressin (AVP) blood level in group I (32%) and a very high level of AVP in group II (311%, P less than 0.05) was determined by RIA. The exposure to hypothermia did not influence the AVP plasma level. The thyroid hypofunction was revealed morphometrically in both hypophysectomized groups. Nevertheless, cooling stimulated the thyroid glands in rats of both experimental groups, like it was in the control. Thus, there is no evidence that thyroid gland reaction to hypothermia is affected by AVP. Cooling caused an increase of corticosteroid blood and adrenal cortex content in nonoperated control rats as well as in group II, but not in group I of experimental animals. Hence, it may be assumed that when the adenohypophysis is ablated, a high AVP blood level is necessary to realize the adrenal cortex response to hypothermia.     

Parameters of dietary selenium and vitamin E deficiency in growing rabbits.

4 x 5 growing female rabbits (New Zealand White) with an initial live weight of 610 +/- 62 g were fed a torula yeast based semisynthetic diet low in selenium (<0.03 mg/kg diet) and containing <2 mg alpha-tocopherol per kg (group I). Group II received a vitamin E supplementation of 150 mg alpha-tocopherylacetate per kg diet, whereas for group III 0.40 mg Se as Na-selenite and for group IV both supplements were added. Selenium status and parameters of tissue damage were analyzed after 10 weeks on experiment (live weight 2,355 +/- 145 g). Selenium depletion of the Se deficient rabbits (groups I and II) was indicated by a significantly lower plasma Se content (group I: 38.3 +/- 6.23 microg Se/mL plasma, group II: 42.6 +/- 9.77, group III: 149 +/- 33.4, group IV: 126 +/- 6.45) and a significantly lower liver Se content (group I: 89.4 +/- 18.2 microg/kg fresh matter, group II: 111 +/- 26.2) as compared to the Se supplemented groups III (983 +/- 204) and IV (926 +/- 73.9). After 5 weeks on the experimental diets differences in the development of plasma glutathione peroxidase were observed. As compared to the initial status group (45.2 +/- 4.50) pGPx activity in mU/mg protein was decreased in group I (19.1 +/- 7.08), remained almost stable in the vitamin E supplemented group II (46.3 +/- 11.2) whereas an elevated enzyme activity was measured in the Se supplemented groups III (62.4 +/- 23.9) and IV (106 +/- 19.9). In the rabbit organs investigated 10 weeks of Se deficiency caused a significant loss of Se dependent cellular glutathione peroxidase activity (GPx1) of 94% (liver), 80% (kidney), 50% (heart muscle) and 60% (musculus longissimus dorsi) in comparison to Se supplemented control animals. Damage of cellular lipids and proteins in the liver was due to either Se or vitamin E deficiency. However damage was most severe under conditions of a combined Se and vitamin E deficiency. It can be concluded that the activity of plasma glutathione peroxidase is a sensitive indicator of Se deficiency in rabbits. The loss of GPx1 activity indicates the selenium depletion in various rabbit organs. Both selenium and vitamin E are essential and highly efficient antioxidants which protect rabbits against lipid and protein oxidation.     

Direct effects in vivo of angiotensins I and II on the canine sinus node.

The chronotropic responses to angiotensins I and II (5 micrograms in 1 mL Tyrode's solution) injected into the sinus node artery were assessed before and after the intravenous administration of captopril (2 mg/kg) and saralasin (20 micrograms/kg) in anaesthetized dogs. The effects of angiotensin II given intravenously were also observed. The animals (n = 8) were vagotomized and pretreated with propranolol (1 mg/kg, i.v.) to prevent baroreceptor-mediated responses to increases in blood pressure. Injection of angiotensin I into the sinus node artery induced significant increases in heart rate (114 +/- 6 vs. 133 +/- 6 beats/min) and in systemic systolic (134 +/- 13 vs. 157 +/- 14 mmHg; 1 mmHg = 133.3 Pa) and diastolic (95 +/- 10 vs. 126 +/- 13 mmHg) blood pressures. Similar results were obtained when angiotensin II was injected into the sinus node artery, but intravenous injection induced changes in systolic (138 +/- 8 vs. 180 +/- 25 mmHg) and diastolic (103 +/- 8 vs. 145 +/- 20 mmHg) blood pressures only. Captopril induced a significant decrease in systolic (118 +/- 11 vs. 88 +/- 12 mmHg) and diastolic (84 +/- 9 vs. 59 +/- 9 mmHg) blood pressures without affecting the heart rate (109 +/- 6 vs. 106 +/- 6 beats/min). Saralasin produced a significant increase in systolic (109 +/- 7 vs. 126 +/- 12 mmHg) blood pressure only. Increments in heart rate and systolic and diastolic blood pressures in response to angiotensins I and II were, respectively, abolished by captopril and saralasin. It was concluded that angiotensin II has, in vivo, a direct positive chronotropic effect that can be blocked by saralasin.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hypothermic preservation of the rat heart. Comparison of immersion and low-flow perfusion methods: contribution of 31P-NMR spectroscopy

Comparison of rat heart preservation by simple storage in a cardioplegic solution at 4 degrees C (6 hr for group I; 15 hr for group II) and by hypothermic low-flow perfusion of the same solution (0.3 ml min-1, 15 hr: group III) was performed by measuring biochemical and functional parameters and by collecting 31P-NMR spectroscopy data. When compared to control values, adenine nucleotide levels remained unchanged in group I hearts, while glycogen was 45% hydrolyzed and lactate level increased by 700%. Extension of heart immersion to 15 hr (group II) led to breakdown of ATP (-77%), of the sum of adenine nucleotides (-27%), and of glycogen (-77%), whereas lactate accumulation reached 900% of the control value. Functional recovery, measured at the end of a 60-min reperfusion was less than 10% in group II hearts when compared to group I hearts. This dramatic development was completely avoided by hypothermic low-flow perfusion (group III). 31P-NMR data showed that phosphocreatine was completely degraded in all groups of preserved hearts. Low-flow perfusion limited cellular acidosis. The ATP/Pi (Pi = inorganic phosphate) ratio calculated from NMR data was lower for group II hearts (0.04 +/- 0.01, n = 6) than for group I hearts (0.29 +/- 0.12; n = 6) or group III hearts (0.19 +/- 0.09; n = 6) and could constitute a convenient bioenergetic index to predict the capability of the heart to recover satisfactory contractility following a preservation period.     

Cardiac acetylcholine concentration in the mouse

We measured cardiac acetylcholine (ACh) in mice using four different methods. The mice in the in vivo irradiation group received microwave irradiation and then the hearts were removed. The animals in the in vitro irradiation group were decapitated and only the hearts were irradiated. The animals in the non-frozen group were decapitated and ACh was measured soon after the removal of the heart. The animals in the frozen group were decapitated and the hearts were frozen. There were significant differences in ACh concentrations between the in vivo irradiation group and the other groups. We also measured the ACh concentrations in both atria and ventricles after the mice were irradiated while alive. The atrial ACh concentration 1.70 +/- 0.70 nmol/g (mean +/- SD) was significantly higher than the ventricle concentration 1.07 +/- 0.30. We concluded the microwave irradiation of animals was suitable method of sacrifice for the measurement of cardiac ACh.     

Sex differences in the development of angiotensin II-induced hypertension in conscious mice

Sex has an important influence on blood pressure (BP) regulation. There is increasing evidence that sex hormones interfere with the renin-angiotensin system. Thus the purpose of this study was to determine whether there are sex differences in the development of ANG II-induced hypertension in conscious male and female mice. We used telemetry implants to measure aortic BP and heart rate (HR) in conscious, freely moving animals. ANG II (800 ng.kg(-1).min(-1)) was delivered via an osmotic pump implanted subcutaneously. Our results showed baseline BP in male and female mice to be similar. Chronic systemic infusion of ANG II induced a greater increase in BP in male (35.1 +/- 5.7 mmHg) than in female mice (7.2 +/- 2.0 mmHg). Gonadectomy attenuated ANG II-induced hypertension in male mice (15.2 +/- 2.4 mmHg) and augmented it in female mice (23.1 +/- 1.0 mmHg). Baseline HR was significantly higher in females relative to males (630.1 +/- 7.9 vs. 544.8 +/- 16.2 beats/min). In females, ANG II infusion significantly decreased HR. However, the increase in BP with ANG II did not result in the expected decrease in HR in either intact male or gonadectomized mice. Moreover, the slope of the baroreflex bradycardia to phenylephrine was blunted in males (-5.6 +/- 0.3 to -2.9 +/- 0.5) but not in females (-6.5 +/- 0.5 to -5.6 +/- 0.3) during infusion of ANG II, suggesting that, in male mice, infusion of ANG II results in a resetting of the baroreflex control of HR. Ganglionic blockade resulted in greater reduction in BP on day 7 after ANG II infusion in males compared with females (-61.0 +/- 8.9 vs. -36.6 +/- 6.6 mmHg), suggesting an increased contribution of sympathetic nerve activity in arterial BP maintenance in male mice. Together, these data indicate that there are sex differences in the development of chronic ANG II-induced hypertension in conscious mice and that females may be protected from the increases in BP induced by ANG II.     

Mechanical combined heart supporting system for prevention of irreversible ventricular fibrillation after experimental cardiogenic shock.

To determine whether haemodynamic effective support of the failing heart can prevent spontaneous irreversible ventricular fibrillation (IVF) after experimental cardiogenic shock, 63 open chest dogs were assigned randomly into four groups--two control groups (combined heart failure--CHF) and two MCHSS-treated (combined heart failure and non-pulsatile bypass with intraaortic counterpulsation). The CHF was produced by occlusion of the anterior descending coronary artery (group I) or the left circumflex coronary artery (group II) and by an artificial shunt between the pulmonary artery and right atrium. IVF were observed in 10 out of 22 control dogs (group I) and im 17 out of 21 control dogs (group II). In the 20 dogs with the CHF (10 animals in each group) the MCHSS was performed in the course of two hours. During the heart support no IVF were observed in any of the dogs. The difference between the incidence of IVF in the control and treated animals is statistically significant (Chi square = 21.9767 greater than Chi square 0.005).