Ultrastructural changes in the microcirculatory bed and filtration-reabsorption barrier of the kidney during temporary ischemia after unilateral nephrectomy

Ultrastructure of cellular elements of the microcirculatory bed and filtration-reabsorption barrier has been studied in 150 mature white rats, in which vascular fasciculus of the left kidney has been compressed for 30 min, 1-2 h with a subsequent restoration of the blood stream in the organ undergone ischemia on the 3rd, 7th, 14th, 30th, 60th, 180th, 360th days under conditions of the preliminarily right kidney nephrectomy. On the 3rd day after ischemia of the remained kidney for 30 min, structural components of the walls of the glomerular arterioles and those of the filtration-reabsorption barrier undergo certain ultrastructural changes, that with time elapsed (7, 14 days) gradually pass away, and amount of cells with hypertrophic processes increases. Ischemia for 1 h in the remained kidney with subsequent restoration of the blood stream on the 3rd, 7th days produces in the structures mentioned more pronounced destructive changes. During subsequent compensatory hypertrophy (the 30th, 60th days) of the remained kidney after its ischemia, in the microcirculatory bed elements and in the convoluted canal epitheliocytes intracellular regenerative and hyperplastic processes develop. However, ischemia for 2 h in the remained kidney produces severe destructive-necrotic phenomena in ultrastructure of the microcirculatory bed and of the filtration-reabsorption barrier.     

Dysfunction of kidney endothelium after ischemia/reperfusion and its prevention by mitochondria-targeted antioxidant

One of the most important pathological consequences of renal ischemia/reperfusion (I/R) is kidney malfunctioning. I/R leads to oxidative stress, which affects not only nephron cells but also cells of the vascular wall, especially endothelium, resulting in its damage. Assessment of endothelial damage, its role in pathological changes in organ functioning, and approaches to normalization of endothelial and renal functions are vital problems that need to be resolved. The goal of this study was to examine functional and morphological impairments occurring in the endothelium of renal vessels after I/R and to explore the possibility of alleviation of the severity of these changes using mitochondria-targeted antioxidant 10-(6′-plastoquinonyl)decylrhodamine 19 (SkQR1). Here we demonstrate that 40-min ischemia with 10-min reperfusion results in a profound change in the structure of endothelial cells mitochondria, accompanied by vasoconstriction of renal blood vessels, reduced renal blood flow, and increased number of endothelial cells circulating in the blood. Permeability of the kidney vascular wall increased 48 h after I/R. Injection of SkQR1 improves recovery of renal blood flow and reduces vascular resistance of the kidney in the first minutes of reperfusion; it also reduces the severity of renal insufficiency and normalizes permeability of renal endothelium 48 h after I/R. In in vitro experiments, SkQR1 provided protection of endothelial cells from death provoked by oxygen–glucose deprivation. On the other hand, an inhibitor of NO-synthases, L-nitroarginine, abolished the positive effects of SkQR1 on hemodynamics and protection from renal failure. Thus, dysfunction and death of endothelial cells play an important role in the development of reperfusion injury of renal tissues. Our results indicate that the major pathogenic factors in the endothelial damage are oxidative stress and mitochondrial damage within endothelial cells, while mitochondria-targeted antioxidants could be an effective tool for the protection of tissue from negative effects of ischemia.     

Human recombinant erythropoietin protects the striated muscle microcirculation of the dorsal skinfold from postischemic injury in mice

Erythropoietin (EPO) has been proposed as a novel cytoprotectant in ischemia-reperfusion (I/R) injury of the brain, heart, and kidney. However, whether EPO exerts its protection by prevention of postischemic microcirculatory deterioration is unknown. We have investigated the effect of EPO on I/R-induced microcirculatory dysfunctions. We used the mouse dorsal skinfold chamber preparation to study nutritive microcirculation and leukocyte-endothelial cell interaction in striated muscle of the dorsal skinfold by in vivo fluorescence microscopy before 3 h of ischemia and during 5 days of reperfusion. Animals were pretreated with EPO (5,000 U/kg body wt) 1 or 24 h before ischemia. Vehicle-treated I/R-injured animals served as controls. Additional animals underwent sham operation only or were pretreated with EPO but not subjected to I/R. I/R significantly (P < 0.05) reduced functional capillary density, increased microvascular permeability, and enhanced venular leukocyte-endothelial cell interaction during early reperfusion. These findings were associated with pronounced (P < 0.05) arteriolar constriction and diminution of blood flow during late reperfusion. Pretreatment with EPO induced EPO receptor and endothelial nitric oxide synthase expression at 6 h of reperfusion (P < 0.05). In parallel, EPO significantly (P < 0.05) reduced capillary perfusion failure and microvascular hyperpermeability during early reperfusion and arteriolar constriction and flow during late reperfusion. EPO pretreatment substantially (P < 0.05) diminished I/R-induced leukocytic inflammation by reducing the number of rolling and firmly adhering leukocytes in postcapillary venules. EPO applied 1 h before ischemia induced angiogenic budding and sprouting at 1 and 3 days of reperfusion and formation of new capillary networks at 5 days of reperfusion. Thus our study demonstrates for the first time that EPO effectively attenuates I/R injury by preserving nutritive perfusion, reducing leukocytic inflammation, and inducing new vessel formation.     

Rapid force recovery in contracting skeletal muscle after brief ischemia is dependent on O(2) availability.

We tested the hypothesis that contracting skeletal muscle can rapidly restore force development during reperfusion after brief total ischemia and that this rapid recovery depends on O(2) availability and not an alternate factor related to blood flow. Isolated canine gastrocnemius muscle (n = 5) was stimulated to contract tetanically (isometric contraction elicited by 8 V, 0.2-ms duration, 200-ms trains, at 50-Hz stimulation) every 2 s until steady-state conditions of muscle blood flow (controlled by pump perfusion) and developed force were attained (3 min). While maintaining the same stimulation pattern, muscle blood flow was then reduced to zero (complete ischemia) for 2 min. Normal blood flow was then restored to the contracting muscle; however, two distinct conditions of oxygenation (at the same blood flow) were sequentially imposed: deoxygenated blood (30 s), blood with normal arterial O(2) content (30 s), a return to deoxygenated blood (30 s), and finally a return to normal arterial O(2) content (90 s). During the ischemic period, force development fell to 39 +/- 6 (SE)% of normal (from 460 +/- 40 to 170 +/- 20 N/100 g). When muscle blood flow was restored to normal by perfusion with deoxygenated blood, developed force continued to decline to 140 +/- 20 N/100 g. Muscle force rapidly recovered to 310 +/- 30 N/100 g (P < 0.05) during the 30 s in which the contracting muscle was perfused with oxygenated blood and then fell again to 180 +/- 30 N/100 g when perfused with blood with low PO(2). These findings demonstrate that contracting skeletal muscle has the capacity for rapid recovery of force development during reperfusion after a short period of complete ischemia and that this recovery depends on O(2) availability and not an alternate factor related to blood flow restoration.     

Vascular wall energetics in arterioles during nitric oxide-dependent and -independent vasodilation.

The objective of this study was to evaluate whether the nitric oxide (NO) released from vascular endothelial cells would decrease vessel wall oxygen consumption by decreasing the energy expenditure of mechanical work by vascular smooth muscle. The oxygen consumption rate of arteriolar walls in rat cremaster muscle was determined in vivo during NO-dependent and -independent vasodilation on the basis of the intra- and perivascular oxygen tension (Po2) measured by phosphorescence quenching laser microscopy. NO-dependent vasodilation was induced by increased NO production due to increased blood flow, whereas NO-independent vasodilation was induced by topical administration of papaverine. The energy efficiency of vessel walls was evaluated by the variable ratio of circumferential wall stress (amount of mechanical work) to vessel wall oxygen consumption rate (energy cost) in the arteriole between normal and vasodilated conditions. NO-dependent and -independent dilation increased arteriolar diameters by 13 and 17%, respectively, relative to the values under normal condition. Vessel wall oxygen consumption decreased significantly during both NO-dependent and -independent vasodilation compared with that under normal condition. However, vessel wall oxygen consumption during NO-independent vasodilation was significantly lower than that during NO-dependent vasodilation. On the other hand, there was no significant difference between the energy efficiency of vessel walls during NO-dependent and -independent vasodilation, suggesting the decrease in vessel wall oxygen consumption produced by NO to be related to reduced mechanical work of vascular smooth muscle.     

Effects of gestational age on myocardial blood flow and coronary flow reserve in pressure-loaded ovine fetal hearts

To test the hypothesis that coronary flow and coronary flow reserve are developmentally regulated, we used fluorescent microspheres to investigate the effects of acute (6 h) pulmonary artery banding (PAB) on baseline and adenosine-enhanced right (RV) and left ventricular (LV) blood flow in two groups of twin ovine fetuses (100 and 128 days of gestation, term 145 days, n = 6 fetuses/group). Within each group, one fetus underwent PAB to constrict the main pulmonary artery diameter by 50%, and the other twin served as a nonbanded control. Physiological measurements were made 6 h after the surgery was completed; tissues were then harvested for analysis of selected genes that may be involved in the early phase of coronary vascular remodeling. Within each age group, arterial blood gas values, heart rate, and mean arterial blood pressure were similar between control and PAB fetuses. Baseline endocardial blood flow in both ventricles was greater in 100 than 128-day fetuses (RV: 341 +/- 20 vs. 230 +/- 17 ml*min(-1)*100 g(-1); LV: 258 +/- 18 vs. 172 +/- 23 ml*min(-1)*100 g(-1), both P < 0.05). In both age groups, RV and LV endocardial blood flows increased significantly in control animals during adenosine infusion and were greater in PAB compared with control fetuses. After PAB, adenosine further increased RV blood flow in 128-day fetuses (from 416 +/- 30 to 598 +/- 33 ml*min(-1)*g(-1), P < 0.05) but did not enhance blood flow in 100-day animals (490 +/- 59 to 545 +/- 42 ml*min(-1)*100 g(-1), P > 0.2). RV vascular endothelial growth factor and Flk-1 mRNA levels were increased relative to controls (P < 0.05) in 128 but not 100-day PAB fetuses. We conclude that in the ovine fetus, developmentally related differences exist in 1) baseline myocardial blood flows, 2) the adaptive response of myocardial blood flow to acute systolic pressure load, and 3) the responses of selected genes involved in vasculogenesis to increased load in the fetal myocardium.     

Ultrastructural changes in the components of the filtration barrier in the glomerular capillaries of a remaining kidney following its temporary ischemia

The components of the filtration barrier of the glomerular capillaries of the rat remaining kidney were studied ultrastructurally 3, 7, 14, 30, 60, 180 and 360 days after exposure to 30 minutes and to 1-2 hours of ischemia. Submicroscopic changes found in the glomerular capillaries and in compensation -adaptive processes occurring in the remaining kidney were ascertained to be dependent on the duration of ischemia and the time elapsed since recirculation in the kidney. After 30-minute ischemia experienced by the remaining kidney the structural alterations in the glomerular capillaries were not remarkable, disappearing 14 days following recirculation, with the emergence by that time of the signs of hyperplasia and hypertrophy of intracellular structures. After raising the time of temporary ischemia of the remaining kidney up to 60 min followed by recirculation, appreciable ultrastructural postischemic disorders were recorded in the components of the filtration barrier of the glomerular capillaries. In addition, the compensation-adaptive processes in the kidney remained suppressed for a longer period of time. All these disorders were particularly demonstrable as a result of 2-hour ischemia. It was also discovered that destructive processes dominated over reparative ones thereby leading to the animals' death at early times of experiment.     

Automatic detection of the carotid artery boundary on cross-sectional MR image sequences using a circle model guided dynamic programming

Background  

Systematic aerobe training has positive effects on the compliance of dedicated arterial walls. The adaptations of the arterial structure and function are associated with the blood flow-induced changes of the wall shear stress which induced vascular remodelling via nitric oxide delivered from the endothelial cell. In order to assess functional changes of the common carotid artery over time in these processes, a precise measurement technique is necessary. Before this study, a reliable, precise, and quick method to perform this work is not present.     

Arterial repair after microvascular anastomosis. Scanning and transmission electron microscopy study

In order to study the morphological aspects of endothelial regeneration and vascular wall reaction after microvascular anastomosis, rat femoral arteries were sectioned and successively sutured (end-to-end anastomosis) with microsurgical techniques. Control arteries and anastomosed vessels (recovered after 1, 4, 7, 14, 21, 30, 60, 120, 180 and 360 days) were studied by means of scanning (SEM) and transmission electron microscopy (TEM). The reendothelialization phenomena started after 7 days and were mainly evident at 21 days. Areas of subendothelial connective tissue with fibrin deposition remained exposed to the blood stream up to 21-30 days. Thrombus formations or post-anastomotic stenosis have been occasionally observed. Regenerating endothelium showed evident morphological differences from the control. These changes mainly consisted of shortened cell length, absence of pinocytotic vesicles, presence of cytoplasmic prolongations, and microvillous proliferations. The arterial wall showed subintimal thickening. The anastomotic site appeared completely covered by new endothelium after 30-60 days. Subintimal vascular wall changes (thickening of the media) as well as slight alterations of endothelial cells (shortened length, reduced number of pinocytotic vesicles) were evident in 60-day vessels. Lumen reduction, due to the protruding of endothelial-covered sutures, was occasionally observed in 60- to 120-day arteries. Endothelial cell morphology normalized after 60-120 days. However, thickening of the media and occasional lumen reduction were observed also after 180-360 days. Although the endothelial regeneration phenomena were clearly evident after 2 weeks, nevertheless the reestablishment of arterial wall took longer time.(ABSTRACT TRUNCATED AT 250 WORDS)     

Augmentation of Neovascularizaiton in Hindlimb Ischemia by Combined Transplantation of Human Embryonic Stem Cells-Derived Endothelial and Mural Cells

Background

We demonstrated that mouse embryonic stem (ES) cells-derived vascular endothelial growth factor receptor-2 (VEGF-R2) positive cells could differentiate into both endothelial cells (EC) and mural cells (MC), and termed them as vascular progenitor cells (VPC). Recently, we have established a method to expand monkey and human ES cells-derived VPC with the proper differentiation stage in a large quantity. Here we investigated the therapeutic potential of human VPC-derived EC and MC for vascular regeneration.

Methods and Results

After the expansion of human VPC-derived vascular cells, we transplanted these cells to nude mice with hindlimb ischemia. The blood flow recovery and capillary density in ischemic hindlimbs were significantly improved in human VPC-derived EC-transplanted mice, compared to human peripheral and umbilical cord blood-derived endothelial progenitor cells (pEPC and uEPC) transplanted mice. The combined transplantation of human VPC-derived EC and MC synergistically improved blood flow of ischemic hindlimbs remarkably, compared to the single cell transplantations. Transplanted VPC-derived vascular cells were effectively incorporated into host circulating vessels as EC and MC to maintain long-term vascular integrity.

Conclusions

Our findings suggest that the combined transplantation of human ES cells-derived EC and MC can be used as a new promising strategy for therapeutic vascular regeneration in patients with tissue ischemia.     

Effects of calcitonin gene-related peptide on renal blood flow in the rat

The effects of alpha-rat calcitonin gene-related peptide (alpha-rCGRP) on systemic and renal hemodynamics and on renal electrolyte excretion were examined in normal anesthetized rats. In one group of rats (n = 7), infusions of alpha-rCGRP at doses of 10, 50, 100, and 500 ng/kg/min for 15 min each produced dose-related and significant decreases in mean arterial pressure from a control of 130 +/- 3 mm Hg to a maximal depressor response of 91 +/- 2 mm Hg. During the first three doses of alpha-rCGRP, renal blood flow progressively and significantly increased from a control of 5.0 +/- 0.3 ml/min to a peak level of 6.3 +/- 0.3 ml/min achieved during the 100 ng/kg/min infusion. With the highest infusion rate of 500 ng/kg/min, renal blood flow fell below the control level to 4.5 +/- 0.2 ml/min (P less than 0.05). The responses in renal blood flow and mean arterial pressure were associated with reductions in renal vascular resistance. After cessation of alpha-rCGRP infusions, arterial pressure, renal blood flow, and renal vascular resistance gradually returned toward the baseline values. In another group of rats (n = 9), infusion of alpha-rCGRP for 30 min at 100 ng/kg/min produced a significant reduction in urinary sodium excretion from 0.28 +/- 0.06 to 0.14 +/- 0.5 muEq/min (P less than 0.05). Urine flow and urinary potassium excretion also appeared to decrease, but the changes were not significantly different (P greater than 0.05) from their respective baselines. These results demonstrate that alpha-rCGRP is a potent and reversible hypotensive and renal vasodilatory agent in the anesthetized rat. The data also suggest that alpha-rCGRP may have significant effects on the excretory function of the kidney.     

Differential effects of acute thermal injury on rat splanchnic and renal blood flow and prostanoid release

This study examines the hypothesis that acute thermal injury decreases renal and splanchnic blood flow which correlates with altered endogenous vasodilator eicosanoid release. Anesthetized male Wistar rats were subjected to sham or a non-resuscitated 30% total body surface area burn. At 1, 2, 4, 8, and 24 h post-burn mean arterial pressure as well as superior mesenteric and renal artery in vivo blood flow were measured. The superior mesenteric and renal arteries were cannulated and perfused in vitro with their end organs with Krebs buffer (pH 7.4, 37°C). Renal and splanchnic 6-keto-PGF_1α (PGI₂), PGE₂, and thromboxane B₂ (TXB₂) release were measured by EIA at 15 min of perfusion. Renal and superior mesenteric artery blood flow decreased by 40% or more at 1 and 2 h post-burn despite mean arterial pressure remaining unchanged. The major eicosanoids released were PGI₂ from the splanchnic bed and PGI₂ and PGE₂ from the kidney. Splanchnic PGI₂ and TXB₂ release and renal TXB₂ increased 2–3 fold at 1 h post-burn but returned to the sham level at 2 h post-burn. By 24 h post-burn the vasodilator eicosanoids were increased in both the splanchnic and renal vascular beds. These data show that decreased renal and splanchnic blood flow was associated with increased endogenous release of the potent vasoconstrictor TXB₂. By 2 h post-burn, renal and splanchnic blood flow began returning toward the sham level as endogenous release of TXB₂ from both organs fell to sham levels. These data suggest that increased endogenous release of TXB₂ may contribute to the short-term decrease in renal and splanchnic blood flow in the immediate post-burn period and thus may contribute to ischemia of both vascular beds.     

The effect of glucagon on glomerular filtration rate in dogs during reduction of renal blood flow.

Glucagon in small intravenous (i.v.) doses markedly increases glomerular filtration rate (GFR) in normal anesthetized dogs. In this study, the effects of glucagon 5 mug/min (i.v.) on renal hemodynamics was tested in four canine models of acute pre-renal failure (hemorrhage, barbiturate overdose; renal arterial clamping and renal arterial infusions of noradrenaline) and in a model of unilateral acute tubular necrosis at 4 h and 6-7 days following completion of the ischemic insult. Following hemorrhage and barbiturate excess, with arterial blood pressure maintained at 65-70 mm Hg, whole-kidney GFR and clearance rate of p-aminohippurate decreased by 50-70%. During this reduction of perfusion pressure, the subsequent infusion of glucagon increased GFR by 90-130%. In models where arterial pressure was normal during the period of ischemia (clamping and noradrenaline infusion), not only did glucagon significantly increase renal perfusion, but the ischemic kidney proved to be far more sensitive to the hemodynamic effects of glucagon (delta GFR - 120-160%) than the contralateral control (deltaGFR = 30-40%). In three dogs completely anuric following renal arterial clamping, glucagon was able to improve blood flow and restart urine formation. Glucagon, but not dopamine, was able to simulate the beneficial effects of hypertonic mannitol on renal function in dogs with hemorrhagic hypotension. Glucagon was without effect in established acute tubular necrosis. This study, therefore, indicates that, during renal ischemia, glucagon may be quite effective in preserving urine output and perfusion of the kidneys.     

Impaired nitric oxide-mediated vasodilation in transgenic sickle mouse

Transgenic sickle mice expressing human beta(S)- and beta(S-Antilles)-globins show intravascular sickling, red blood cell adhesion, and attenuated arteriolar constriction in response to oxygen. We hypothesize that these abnormalities and the likely endothelial damage, also reported in sickle cell anemia, alter nitric oxide (NO)-mediated microvascular responses and hemodynamics in this mouse model. Transgenic mice showed a lower mean arterial pressure (MAP) compared with control groups (90 +/- 7 vs. 113 +/- 8 mmHg, P < 0.00001), accompanied by increased endothelial nitric oxide synthase (eNOS) expression. N(G)-nitro-L-arginine methyl ester (L-NAME), a nonselective inhibitor of NOS, caused an approximately 30% increase in MAP and approximately 40% decrease in the diameters of cremaster muscle arterioles (branching orders: A2 and A3) in both control and transgenic mice, confirming NOS activity; these changes were reversible after L-arginine administration. Aminoguanidine, an inhibitor of inducible NOS, had no effect. Transgenic mice showed a decreased (P < 0.02-0.01) arteriolar dilation in response to NO-mediated vasodilators, i.e., ACh and sodium nitroprusside (SNP). Indomethacin did not alter the responses to ACh and SNP. Forskolin, a cAMP-activating agent, caused a comparable dilation of A2 and A3 vessels ( approximately 44 and 70%) in both groups of mice. Thus in transgenic mice, an increased eNOS/NO activity results in lower blood pressure and diminished arteriolar responses to NO-mediated vasodilators. Although the increased NOS/NO activity may compensate for flow abnormalities, it may also cause pathophysiological alterations in vascular tone.     

L-arginine protects from ischemia-reperfusion-induced endothelial dysfunction in humans in vivo.

It has been shown that nitric oxide (NO) protects from myocardial ischemia-reperfusion injury in animal models. The present study investigated whether administration of the NO substrate l-arginine protects against ischemia-reperfusion-induced endothelial dysfunction in humans. Forearm blood flow was measured with venous occlusion plethysmography in 16 healthy male subjects who were investigated on two occasions. Forearm ischemia was induced for 20 min followed by 60-min reperfusion. With the use of a crossover protocol, the subject received a 15-min intrabrachial artery infusion of l-arginine (20 mg/min) and vehicle (saline, n = 12 or d-arginine, n = 4) starting at 15 min of ischemia on two separate occasions. Compared with preischemia, endothelium-dependent increase in forearm blood flow induced by intra-arterial acetylcholine (3-30 microg/min) was significantly impaired at 15 and 30 min of reperfusion when the subjects received saline (P < 0.001). When the subjects received l-arginine, the acetylcholine-induced increase in forearm blood flow was not significantly affected by ischemia-reperfusion. The recovery of endothelium-dependent vasodilatation at 15- and 30-min reperfusion was significantly greater after administration of l-arginine than after saline (P < 0.05). d-Arginine did not affect the response to acetylcholine. Endothelium-independent vasodilatation to nitroprusside was not affected during reperfusion. These results demonstrate that the NO substrate l-arginine significantly attenuates ischemia-reperfusion-induced endothelial dysfunction in humans in vivo. This suggests that l-arginine may be useful as a therapeutic agent in the treatment of ischemia-reperfusion injury in humans.     

Biomechanical adaptation of porcine carotid vascular smooth muscle to hypo and hypertension in vitro

Previous research in arterial remodeling in response to changes in blood pressure seldom included both hyper- and hypotension. To compare the effects of low and high pressure on arterial remodeling and vascular smooth muscle tone and performance, we have utilized an in vitro model. Porcine carotid arteries were cultured for 3 days at 30 and 170mmHg and compared to controls cultured at 100mmHg for 1 and 3 days. On the first and last day of culture, pressure-diameter and pressure-wall thickness curves were measured under normal smooth muscle tone using a high-resolution ultrasonic device. Last-day experiments included measurements where vascular smooth muscle was contracted or totally relaxed. From the data wall cross-sectional area, Hudetz elastic modulus and a contraction index related to the diameter reduction under normal smooth muscle tone were calculated. We found that although wall cross-sectional area (indicating wall mass) did not change much, Hudetz elastic modulus was significantly reduced in the 3-day hypotension group. Inspection of the wall contraction index suggests that this is due to a reduction in the vascular smooth muscle tone. Further, the peak of contraction index was found to be shifted to higher pressures in the 3-day 170mmHg group. We conclude that vascular smooth muscle performance adapts to both hypo- and hypertension at short time scales and can alter the biomechanics of the vascular wall in vitro.     

The combined effects of dopamine (DA) and the DA antagonists EGYT-2509, chlorpromazine and haloperidol on the kidney function

In anaesthetized dogs renal function was investigated in four successive 20-min periods in four experimental series. (1) In the first series following the first period (serving as control) 2.5 micrograms/kg/min of dopamine (DA) dissolved in 0.5 ml/min of Ringer's solution was infused into the left renal artery (period 2), than during periods 3 and 4. It was found that first (period 2) and second (period 3) doses of DA induced a significant decrease of about 20-30% in renal vascular resistance, and an increase of about 15-25% in renal blood flow. At the same time, systemic arterial blood pressure fell by 10%. The other investigated parameters of the left kidney (Cinulin, CPAH, sodium, potassium and water excretion) did not differ from the respective parameters of the intact right kidney. (2) In the second experimental series following the first period (prior to period 2) 1.0 mg/kg of the DA antagonist EGYT 2509 was administered intravenously. Prior to the period 3 again 1.0 mg/kg of EGYT 2509 and prior to period 4 2.0 mg/kg of EGYT 2509 was given intravenously. During periods 2 through 4 2.5 micrograms/kg/min of DA was infused into the left renal artery. It could be ascertained that EGYT 2509 abolished the renal effects of DA while not inducing any decrease in arterial blood pressure. (3) In the third experimental series, following the control period, prior to periods 2,3 and 4, 1.0 mg/kg, 1.0 mg/kg and 2.0 mg/kg chlorpromazine respectively, was administered i.v. followed by the infusion of DA into the left renal artery. After the administration of chlorpromazine arterial blood pressure and renal vascular resistance fell concomitantly and DA failed to induce any further changes in these parameters. According to our experiments chlorpromazine abolishes the effect of DA on kidney function. (4) In the fourth series, prior to DA infusion the dogs were given 0.5 mg/kg (period 2) then again 0.5 mg/kg and finally 1.0 mg/kg of haloperidol intravenously. Haloperidol decreased arterial blood pressure as well as renal vascular resistance, thus renal blood flow did not change. Renal blood flow could then be increased by DA infused into the left renal artery. It seems that haloperidol could not abolish the vascular effects of DA in the kidney. Our experiments indicate that substance EGYT 2509 possesses the most marked dopaminergic antagonistic effect, chlorpromazine had also been effective, while haloperidol had proved to be practically ineffective.     

缺血再灌后血管内皮空泡的形成与内皮的损伤

目的：在活体上探讨缺血再灌后血灌内上细胞损伤及白细胞、血小板与内皮之间粘附的变化。方法：用失血及与再回输血液造成缺血再灌流模型,在高倍显微镜下观察肠系膜微血管内皮损伤及血细胞粘附的变化。结果：缺血再灌后1－3h细静脉、集合毛细血管内出现白细胞、血小板的粘附,血管内皮水肿、管壁增厚,有的血管内皮细胞的胞浆形成圆丘形的空泡,空泡从血管内皮突入管胺、空泡直径10－30μm多出现的细动脉内,在同一根血管内可同时出现几个空泡,大的空泡几科占据血管腔的2／3。结论：缺血再灌后血管内皮水肿及空泡形成,显示内皮细胞的严重损伤。     

Protective effects of leukopenia and tissue plasminogen activator in microvascular ischemia-reperfusion injury

Ischemia shifts the anticoaugulant/procoagulant balance of the endothelium in favor of activation of coagulation. We studied whether cheek pouch microcirculation of leukopenic hamsters was protected by tissue plasminogen activator (tPA) (50 microg/100 g body wt) against ischemia-reperfusion injury. Adherent leukocytes, total perfused capillary length (PCL), permeability increase, and arteriolar and venular red blood cell (RBC) velocity were investigated by fluorescence microscopy. Measurements were made at control, 30 or 60 min of ischemia, and at 30 or 60 min of reperfusion. Hamsters were made leukopenic by treatment with cyclophosphamide (20 mg/100 g body wt ip, 4 days before the experiment), which decreased circulating leukocyte count by 85-90%. Leukopenic hamsters undergoing 30 min of ischemia followed by 30 min of reperfusion showed no significant decrease in PCL or increased permeability. Leukopenic hamsters undergoing 60 min of ischemia followed by 60 min of reperfusion presented a significant decrease in microvascular perfusion where PCL was 28 +/- 7% of baseline, low-flow conditions, and increased permeability. In leukopenic hamsters treated with tPA there was complete protection of capillary perfusion with no significant changes in permeability or arteriolar and venular RBC velocity. In conclusion, thrombus formation may be an additional and independent factor that with leukocyte-mediated mechanisms determines ischemia-reperfusion injury.     

Relationship between blood flow and steroidogenesis in the rabbit corpus luteum

Blood flow in the corpus luteum of the pseudopregnant rabbit was measured with tracer-labelled microspheres before and at 1 and 3 h after saline treatment (N = 8) or after inhibition of progesterone synthesis with aminoglutethimide (N = 10). Before treatment luteal blood flow (29.5 +/- 3.9 ml/min.g-1 (mean +/- s.e.m.] was much higher than blood flow to other tissues (ovarian stroma = 2.9 +/- 0.6; uterus = 0.5 +/- 0.1; adrenal gland = 2.6 +/- 0.2 ml/min.g-1). Aminoglutethimide reduced serum progesterone by 60% within 1 h but luteal blood flow was unchanged (26.2 +/- 3.5 ml/min.g-1). At 3 h after aminoglutethimide, serum progesterone remained low and luteal blood flow was slightly reduced to 22.5 +/- 3.4 ml/min.g-1. This reduction was associated with a significant decline in mean arterial blood pressure which resulted in luteal vascular resistance being unaltered by aminoglutethimide treatment. Further analysis of these data indicated that serum progesterone concentration was not significantly correlated with blood flow to the corpora lutea or with blood flow to other tissues. In contrast, mean arterial blood pressure was highly correlated with blood flow to the corpus luteum (r = 0.80; P less than 0.001) but not to the ovarian stroma (r = 0.04), or adrenal gland (r = 0.06). These results indicate that luteal blood flow is not acutely responsive to changes in luteal progesterone production and suggest that luteal blood flow changes passively with changes in arterial blood pressure.