摘要:

We treated 20-week-old spontaneously hypertensive rats (SHR) with either placebo or hydralazine, reserpine and hydrochlorothiazide for 1 month. Mean arterial pressure in treated SHR averaged 113 ± 7 mm Hg (mean ± SE), compared to 162 ± 12 mm Hg in animals receiving placebo (p < 0.01). Glomerular filtration rate (GFR) and sodium excretion were similar in both groups. In isolated perfused kidneys, the GFR and sodium excretion were significantly greater in the treatment group than in the placebo group at a perfusion pressure of 140 mm Hg (p < 0.01). Renal vascular resistance (RVR) of kidney from treated SHR was no different from RVR of kidney from placebo SHR. Hydralazine (6 mM) and diazoxide (4 mM) increased the GFR and sodium excretion of isolated SHR kidney perfused at 140 mm Hg (p < 0.05), but decreased RVR significantly (p < 0.05). We conclude that prolonged antihypertensive treatment renders higher GFR values to isolated SHR kidneys perfused at 140 mm Hg, with sodium excretion varying in proportion to the GFR. The addition of vasodilators to the perfusate of isolated SHR kidneys partially reproduced these changes, but only at extremely high concentrations unlike to be attained in vi

ISSN:1420-4096    

DOI:10.1159/000173037

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The ability of the kidney to synthesize urea is of interest and some controversy. We tested the hypothesis that low plasma urea concentrations would stimulate renal urea synthesis, thereby enhancing urinary concentrating ability. We defined a ratio of specific activity of plasma/specific activity of urine (SA ratio) greater than 1.0 as indicative of de novo intrarenal urea synthesis. We studied dogs on 3 dietary regimens: (1) commercial chow ad libitum; (2) restricted rations of the same chow; (3) protein-free diet ad libitum with vitamin/mineral supplement. A significant inverse relationship between plasma urea concentration and SA ratio was seen only in the ration-restricted group, despite the fact that plasma urea concentrations in this group were highest of the three groups. In addition, dogs in this group were more likely to demonstrate renal urea synthesis than dogs in the other groups. Thus, the dog kidney is capable of de novo urea synthesis, but a reduced plasma urea concentration does not necessarily stimulate this metabolic activity. Other factors in addition to the plasma urea concentration appear to be involved in the regulation of renal urea synthesis.

ISSN:1420-4096    

DOI:10.1159/000173038

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

In the present study natriuretic activity and digoxin-like immunoreacting activity (DLIA) were determined in small molecular weight (MW) fractions of urine from healthy subjects during low (35 mmol/day) and high ( > 400 mmol/day) sodium intake by bioassay and by a radioimmunoassay for digoxin, respectively. After gel filtration of urine on a Sephadex®G-25 column the natriuretic activity appeared in the post-salt fraction SIV, whereas DLIA was present in small amounts in the salt fraction SIII and, with consistently higher activity, in the post-salt fraction SIV. Natriuretic activity significantly increased and DLIA decreased in fraction SIV with high sodium intake, but total urinary excretion of DLIA remained unaltered during changes in sodium intake. In addition, anion-exchange and reverse-phase chromatography revealed that DLIA is not specifically related to the natriuretic activity but also reflects unspecific binding of various urine constituents to this digoxin antibody. Although the antibody binds a natriuretic material, this radioimmunoassay is thus unsuitable to determine the endogenous natriuretic activity in urine fractions. Whereas they elute differently on reverse-phase chromatography, amino acid analyses revealed that both the natriuretic factor directly purified from the post-salt fraction SIV and the natriuretic material bound to the digoxin antibody have in common four amino acids at similar molar ratios. The physicochemical properties as evidenced by chromatographic and electrophoretic studies as well as enzymatic inactivation suggest that the low MW natriuretic factor(s) in human urine may be associated with a small peptide(s) of weak acidic nature

ISSN:1420-4096    

DOI:10.1159/000173039

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The effects of basic and neutral amino acids on the reabsorption of 125I-lysozyme by the renal proximal tubule were examined in rats. In whole animal experiments control animals were given an intravenous (i.v.) injection of 125I-lysozyme alone while experimental animals received an i.v. injection of either a basic or a neutral amino acid prior to the injection of 125I-lysozyme. In control animals the renal content of 125I-lysozyme 30 min after injection was 35% of the injected dose. After injection of basic amino acids there was a significant decrease in the renal uptake of lysozyme. There was no effect of neutral amino acids on the reabsorption of lysozyme. In microperfusion experiments proximal convoluted tubules were perfused in vivo for 3 min with a solution containing 125I-lysozyme and either lysine or alanine. In tubules perfused with lysine there was a significant decrease in the reabsorption of lysozyme, whereas alanine had no effect on lysozyme uptake. Electron microscope autoradiography revealed that lysozyme was located in endocytic vesicles and lysosomes in both experimental groups. However, the autoradiographic grain density was significantly decreased in tubules perfused with lysine as compared with those perfused with alanine. These findings demonstrate that basic amino acids inhibit the reabsorption of the cationic protein lysozyme by the proximal tubule cells.

ISSN:1420-4096    

DOI:10.1159/000173040

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The functional role of H1 and H2 receptors in mediating the effects of histamine on renal hemodynamics and tubular function was investigated in anesthetized dogs. Histamine, infused directly into the renal artery, caused decreases in renal vascular resistance and increases in total renal blood flow without significant changes in mean arterial blood pressure or glomerular filtration rate. These hemodynamic effects of histamine were inhibited by the H2-receptor antagonist, cimetidine, but not by the H1-receptor antagonist, tripelennamine. Histamine also caused increases in fractional urine flow and the fractional excretion of sodium and calcium with a concomitant decrease in urine/plasma osmolality. These tubular effects of histamine were antagonized by both tripelennamine and cimetidine. Histamine-induced increases in the fractional excretion of potassium were blocked only by tripelennamine. These results suggest that (1) both H1 and H2 receptors mediate the effects of histamine on urinary dilution and tubular reabsorption; (2) H2 receptors mediate the effects of histamine on renal hemodynamics, indicating that H2 receptors are present in the renal vasculature, and (3) H1 receptors may exist in the renal tubules.

ISSN:1420-4096    

DOI:10.1159/000173041

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The effect of verapamil, a Ca++ antagonist drug, on renal function and proximal fluid reabsorption in normal and hypertensive (GΠ) rats was studied. During intravenous infusion of verapamil, mean arterial pressure (MAP) fell significantly in both groups, 23% more in hypertensive than in normotensive rats. Glomerular filtration rate (GFR) was significantly higher in hypertensive rats and also increased significantly in this group during verapamil infusion. Effective renal plasma flow (ERPF) was similar in both groups and did not change significantly during verapamil infusion. The increase in urine flow, Na+ and Ca++ excretion was higher in hypertensive than in normotensive rats during verapamil infusion. When 10-5M verapamil was added to the luminal perfusate of proximal tubules, fluid reabsorption was reduced to 64% in normotensive and to 42% in hypertensive rats. When added to capillary perfusate, fluid reabsorption was almost completely but reversibly inhibited (92% in normotensive and 83% in hypertensive rats). Our findings indicate a direct effect of verapamil on renal Na+ and possibly also on Ca++ reabsorption, suggesting involvement of the Na+-Ca++ countertransport system. The greater effect of verapamil on Na+ excretion in hypertensive rats was not due to increased action on proximal Na+ reabsorption

ISSN:1420-4096    

DOI:10.1159/000173042

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The proportion of glomerular basement membrane (GBM) solubilised following pepsin treatment increased with age when the digestion was carried out at 4°C, but remained constant at 50% of the membrane when the digestion was carried out at 10°C irrespective of rat age. Amino-acid analysis of the solubilised material indicated that it became more collagen-like with age, as judged by the increase in glycine, hydroxyproline and hydroxylysine content, if the digestion was carried out at 10 °C. Polyacrylamide gel electrophoresis of pepsin-solubilised material demonstrated that components with apparent molecular weights of 180,000, 160,000 and 130,000 increased in intensity with age. Components with apparent molecular weights < 85,000 were only present in pepsin-soluble material prepared from GBM isolated from young rats. The intensity of the bands in the pro-α-region varied with age and some procollagen-like material was not solubilised by pepsin treatment. These studies confirm that aging of rat GBM is characterised by an increase in the proportion of the collagenous components present in rat

ISSN:1420-4096    

DOI:10.1159/000173043

出版商:S. Karger AG    

年代:1985

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000173044

出版商:S. Karger AG    

年代:1985

数据来源: Karger