The effect of enalapril on glomerular hemodynamics and permselectivity and on subsequent sclerosis was studied in male MWF/Ztm rats which spontaneously develop proteinuria and glomerular structural damage. Untreated group 1 and enalapril-treated group 2 (50 mg/liter, in the drinking water) underwent micropuncture studies after 2 mo of observation. After the ...

The effects of a moderate reflex activation of the sympathetic nervous system on renal blood flow (RBF) and glomerular filtration rate (GFR) were studied in 29 experiments on seven conscious foxhounds. Autoregulation parameters were derived by a stepwise reduction of renal artery pressure of 10-mmHg decrements. An occlusion of both ...

1. The effects of reduction in renal blood flow (RBF) on urinary acidification and proximal tubule H+ ion secretion were studied after partial aortic clamping in rats. 2. Acute reduction of the renal perfusion pressure (from 109 +/- 3.88 to 77.4 +/- 1.05 mmHg) decreased both inulin and PAH (p-aminohippurate) ...

The effect of atrial natriuretic factor [ANF-(1-28); 0.25 microgram.kg-1.min-1] on tubuloglomerular feedback (TGF) and the efficiency of renal blood flow (RBF) autoregulation was determined in anesthetized euvolemic rats. In microperfusion studies, ANF dramatically inhibited (greater than 80%) feedback-mediated decreases in single-nephron glomerular filtration rate (SNGFR) and stop-flow pressure (Psf) when ...

Glomerular capillaries are perfused at a high hydraulic pressure. Since the capillary mesangium interface presents no morphologically apparent pressure barrier, it is suggested that the hydraulic pressure in the mesangium may also be high. This paper analyzes the structures in the glomerular tuft that are capable of counteracting the distending ...

Renal arteriolar diameters were measured, using microvascular resin casts, in two hyperfiltration models of rats: the remnants kidney of subtotal nephrectomy (NX) and streptozotocin-induced diabetic kidney (DM). In the NX, the blood pressure was elevated, urinary protein excretion was markedly increased and glomeruli were severely damaged. In the DM, although ...

Videomicroscopic and micropuncture techniques were utilized to determine segmental microvascular responses of in vitro blood-perfused juxtamedullary nephrons to step changes in renal arterial perfusion pressure (PP). At a PP of 104 +/- 2 mmHg, inside diameters of arcuate arteries (ARC), interlobular arteries (ILA), and afferent arterioles (AFF) averaged 68.6 +/- ...

1. Over the last 5 years we have given intravenous gludopa in man and established its effects on the kidney. 2. At doses of 12.5 to 100 micrograms kg-1 min-1 it is natriuretic and also tends to increase renal blood flow and glomerular filtration. Despite the natriuresis, plasma renin activity ...

The effect of kallidin (lysyl-bradykinin) on the urinary recovery of sodium-22 was examined in anesthetized, volume-expanded rats. Sodium-22 was microinfused into the lumen of late proximal convoluted tubules with and without kallidin (100 pg/ml). Kallidin enhanced mean sodium-22 recovery from a control of 2.24 +/- 0.29% to 6.22 +/- 1.30% ...

We investigated the effects of elevated venous pressure, Pv, (up to 140 mmHg) on the solvent drag reflection coefficient, sigma f, for protein and on the capillary filtration coefficient, CFC, in the isolated cat hindlimb perfused at constant flow. The perfusate contained 30% cat plasma and the remainder was a ...

The glomerular dynamic correlates of failed filtration were studied in volume replete rats with established glycerol-induced acute renal failure (ARF). Over one-half of all nephrons formed virtually no filtrate, while the single nephron glomerular filtration rate (SNGFR) of fluid-filled nephrons, measured at the glomerulotubular junction to preclude the possibility of ...

Microradiography of nephrons in kidneys perfusion-fixed with glutaraldehyde permits examination of large numbers of nephrons. This technique was applied to rabbits between one and 14 days following unilateral ureteral ligation. Kidneys without ureteral occlusion served as controls. By two days after ureteral obstruction there was dilatation of the ducts of ...

Under normal conditions glomerular blood flow and glomerular capillary hydrostatic pressure and hydrostatic pressure gradient are regulated within a narrow range in spite of variations in volume status and blood pressure. Glomerular ultrafiltration rate is normally regulated by the hydrostatic pressure gradient, the systemic oncotic pressure, the rate of nephron ...

The effect of the converting enzyme inhibitor (CEI) enalapril was assessed in Munich-Wistar rats with established adriamycin nephrosis. Rats were given a single dose of adriamycin and one month later divided into four groups matched for albuminuria, blood pressure, and plasma albumin concentration. Groups 1 and 3 remained untreated while ...

Clinical and experimental observations suggest an association between hypercholesterolemia and progressive glomerular injury. In the main, most investigators have assumed that hypercholesterolemia induces an atherosclerotic process in the renal microvasculature analogous to that well recognized in larger vessels. The evidence for this line of reasoning is well described in other ...

Administration of beta-blockers is frequently associated with decreases in both renal plasma flow and glomerular filtration rate (GFR). Tertatolol, a new non-selective beta-blocker, has demonstrated similar systemic effects to other conventional beta-blockers, but tertatolol produces increases in both renal plasma flow and glomerular filtration rate. To evaluate the renal hemodynamic ...

To evaluate the contribution of beta 1-2-adrenergic receptor stimulation to the regulation of single-nephron glomerular filtration rate (SNGFR), we examined by micropuncture techniques the effects of systemic and intrarenal infusion of isoproterenol on glomerular hemodynamics in plasma volume-expanded Munich-Wistar rats. Isoproterenol infused systemically was consistently associated with an elevation in ...

To assess the quantitative relation between exposure to airborne cadmium and various markers of renal tubular and glomerular function, 45 male workers employed at a plant that recovers cadmium from industrial waste and 32 male hospital workers of similar age and geographical location were examined. Cumulative external exposure to airborne ...

The renal effects of a single intravenous dose of two different E. coli lipopolysaccharides (LPS 0111:B4 and LPS 0127:B8), at the same dose of 100 micrograms/kg, were evaluated in euvolemic Munich-Wistar (MW) rats by whole kidney clearance techniques and micropuncture studies. Following LPS infusion, a significant decrease (8%) in mean ...

1. The effects of acute unilateral renal denervation were examined in 17 anaesthetized rats. Renal haemodynamic changes were monitored using standard clearance techniques. Lithium clearance was used to assess fractional proximal sodium and water reabsorption. 2. Denervation resulted in ipsilateral renal vasodilatation with marked natriuresis and diuresis, a small increase ...

The glomerular size-selective properties in a patient with "hyponatremic hypertensive syndrome" were investigated before and after administration of the angiotensin-converting enzyme inhibitor enalapril. Hyponatremic hypertensive syndrome is a rare condition of renovascular hypertension characterized by electrolyte abnormalities (hyponatremia, hypokalemia), polyuria, and high renin activity. In this patient a marked increase ...

Systemic hypertension accelerates the progression of glomerular injury. Studies in experimental animals indicate that the beneficial effects of antihypertensive agents may relate to their intrarenal haemodynamic consequences, and specifically to their effects on the arteriolar resistances. Relative afferent arteriolar vasodilation allows transmission of systemic pressure into the glomerular capillary network; ...

The tubuloglomerular feedback (TGF) system is less sensitive after extracellular volume expansion (VE). In rats with partial ureteral obstruction, however, we have previously found increased TGF sensitivity during such expansion. Thromboxane A2 (TXA2) has been reported to be increased in the hydronephrotic kidney, and the present study was undertaken to ...

The microvascular mechanisms responsible for oedema formation following the administration of calcium antagonists were studied in 10 healthy volunteers given intravenous felodipine and vehicle in a double-blind crossover trial. Plethysmography and laser Doppler flowmetry were used to measure microvascular parameters. Felodipine increased both skin and forearm blood flow. Due to ...

Adrenergic activity regulates renal function by several mechanisms. Renal nerves not only exert vasoconstrictor functions but also may influence glomerular hemodynamics by beta-adrenergic activity, especially via the effects on renin angiotensin activity. Little is known of the specific glomerular hemodynamic alterations resulting from beta 1-adrenergic blockade. Current studies examined the ...

Preliminary hemorheologic studies using clinical filtration techniques on blood cell suspensions have suggested that changes in erythrocyte (RBC) deformability occur during left ventricular assist system (LVAS) support. In the biophysics literature, it is generally accepted that the elastic properties of the RBC membrane complex affect the microcirculatory deformability of the ...

Previous experiments have shown oscillations in proximal tubular pressure in halothane-anesthetized rats. Such oscillations should be due to oscillations in flow rate and should cause periodic oscillations in both distal tubular chloride concentration and distal tubular pressure. The purpose of the study was to test these predictions. In halothane-anesthetized Sprague-Dawley ...

Our ability to measure precisely the pressures and flows within the glomerular microcirculation has enabled us to begin to unravel the complex relationship between systemic hypertension and kidney disease. Although a number of factors have been implicated in the development of glomerular sclerosis, one consistent finding has been that glomerular ...

The glomeruli of kidneys subjected to reduced perfusion pressure were examined morphometrically. The left renal artery was narrowed for 30 min in anesthetized dogs with (n = 6) or without (n = 7) converting-enzyme inhibition (captopril). The kidneys were then rapidly fixed by glutaraldehyde perfusion at high flow rate. In ...

The "Gamma Loop" Part I compared a model of rubber tubing to the architecture of the glomerulus with emphasis placed on the observed relationship between the position of the outflow resistance clamp and the perfusion of the loop (1, 2). Part II describes the pressures observed in the different parts ...

In Munich-Wistar rats, a micropipette was inserted into a first-order branch of the left main renal artery and continuously infused with human/porcine endothelin (0.4 ng/min). Micropuncture measurements revealed substantial differences within the cortical microcirculation of the same left kidney: SNGFR was some 35% lower in glomeruli exposed to endothelin compared ...

The capillary filtration coefficient (CFC) in the human forearm, determined with the 'venous occlusion' method, was found to be about 0.005 ml min-1 100 ml-1 soft tissue mmHg-1 when capillary pressure (Pc) was raised by about 30 mmHg, a finding in accordance with previous literature. With gradually smaller increments of ...

To determine whether the accelerated rate of lobe weight gain during severe pulmonary edema is attributed to increased permeability of the microvascular barrier or a loss of tissue forces opposing filtration, the effect of edema on capillary filtration coefficient (Kf,C), interstitial compliance (Ci), and the volume of fluid filtered after ...

The hyperbicarbonatemia of chronic respiratory acidosis is maintained by enhanced bicarbonate reabsorption in the proximal tubule. To investigate the cellular mechanisms involved in this adaptation, cell and luminal pH were measured microfluorometrically using (2",7')-bis(carboxyethyl)-(5,6)-carboxyfluorescein in isolated, microperfused S2 proximal convoluted tubules from control and acidotic rabbits. Chronic respiratory acidosis was ...

1. Twenty-four patients with primary hyperparathyroidism were studied before and 18 restudied 6.5 months (mean) after parathyroidectomy, to investigate the pathogenesis of the hypertension which may accompany this condition. Comparison was made with age-matched patients with essential hypertension and with normotensive control subjects. 2. There was a significant inverse relationship ...

We investigated potentiation of atrial peptide (AP)-induced natriuresis by vasopressin in anesthetized rats. Increasing doses of vasopressin potentiated AP-induced natriuresis in a dose-dependent manner, e.g., sodium excretion during AP administration (290 ng/min) was 0.66 +/- 0.16, 2.02 +/- 0.68, 5.21 +/- 1.38 and 7.08 +/- 1.96 mu eq/min during infusion ...

We evaluated the effects of chronic cyclosporine (CsA) administration on the determinants of nephron filtration rate (SNGFR) using micropuncture techniques (mp) in male Munich-Wistar rats. Animals received CsA (30 mg/kg SQ) in olive oil daily for 8 d before mp. Controls (PFC) were pair fed. SNGFR, glomerular capillary hydrostatic pressure ...

In isolated, dog lung lobes with pulmonary vessels filled with different liquids, we measured the rate of weight gain for 5 or 10 min at constant alveolar and vascular pressures under zone 1 conditions (alveolar pressure greater than vascular pressure). We used six different liquids: syngeneic plasma, whole blood (hematocrit ...

Autoregulation of renal blood flow and filtration rate was studied using micropuncture technique in Munich-Wistar rats with acute water deprivation (AWD) or congestive heart failure (CHF). In the first set of experiments, reduction of renal perfusion pressure to approximately to 70% of its initial value resulted in uncoupling of glomerular ...

Filtrability of a suspension of polymorphonuclear leukocytes (PMNs) was examined in a Nuclepore membrane filtration system utilizing a gradually reduced pressure difference with or without an additional negative pressure. The filtration process was continuously recorded using a TV-video system for data analysis. The PMN content in the filtrate was directly ...

Hypertension is a multifactorial disease that is manifested hemodynamically by an increased total peripheral resistance that is more or less uniformly distributed throughout the organ circulations, especially in its target organs, the brain, heart, and kidney. The vasoconstriction involves venules as well as arterioles. The increased afterload that is imposed ...

Bicarbonate reabsorption by the immature kidney in response to acute acid-base changes was assessed in 50 anesthetized newborn rabbits before the end of nephrogenesis. The normal newborn rabbit (age 5-12 days) is in a state of hypochloremic metabolic alkalosis (PHCO3-, 31.9 +/- 0.6 mmol/l; PCl-, 83.1 +/- 1.0) and excretes ...

To elucidate the mechanisms by which indomethacin lowers proteinuria, we studied 20 patients with the nephrotic syndrome. We performed differential macromolecule clearances before and after 3 days of therapy (150 mg/24 h). The fractional clearances of albumin and immunoglobulin G (IgG) decreased by 42 +/- 7 and 44 +/- 10%, ...

1. The distribution of morphological injury was assessed qualitatively and quantitatively in the perfused rat kidney in vitro at controlled rates of oxygen delivery in the presence of low concentrations of erythrocytes. 2. In control kidneys (total oxygen delivery approximately 32 mumol/min per kidney) no injury was seen in the ...

The effect of prior urinary tract obstruction on total CO2 flux in cortical and medullary collecting tubules was examined using an unilateral ureteral obstruction model and isolated tubule in vitro microperfusion. Tubules were obtained from the control and obstructed kidneys after 1, 2, and 4 days of obstruction. Paired comparison ...

The maximum value of capillary filtration coefficient (CFC) in maximally vasodilated cat skeletal muscle is disputed. It was hypothesized that the wide range of reported values was caused by the inability of gravimetric and volumetric measurements of tissue volume to separate transcapillary filtration from vascular volume changes. Consequently, we developed ...

The present study examines the influence of two angiotensin converting enzyme (ACE) inhibitors, perindopril and captopril, on renal plasma flow and on autoregulation of glomerular filtration in anaesthetized rats during reduction of renal perfusion pressure to 100, 90 and 80 mmHg. Groups 1 and 3 had a normal sodium intake ...

The tubuloglomerular feedback (TGF) mechanism was evaluated in the nonclipped kidney of Goldblatt hypertensive rats from both stop flow pressure (SFP) and single nephron glomerular filtration rate (SNGFR) responses to step increases in late proximal perfusion rate from 0 to 40 nl/min. During control conditions, increases in late proximal perfusion ...

Calcium antagonists decrease the ability of the kidney to autoregulate renal blood flow (RBF) and glomerular filtration rate (GFR). Therefore, when afferent renovascular resistance is elevated, as in essential hypertension, there is a resultant increase in RBF and GFR with the administration of calcium antagonists. These agents also induce a ...

Systemic hypertension complicates the course of most patients with chronic renal failure and accelerates the progression of experimental and clinical glomerular disease. Based on recent experimental studies, it is suggested that at similar levels of systemic hypertension, glomerular injury only develops when pre-glomerular resistances are ineffective, thus allowing the development ...