ISSN:1420-4096    

DOI:10.1159/000172638

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Brattleboro rats with diabetes insipidus (DI) exhibit an impaired urinary concentrating ability in response to exogenous vasopressin (AVP) and a decreased AVP-sensitive adenylate cyclase (AC) in homogenates of kidney medulla. To further analyze this phenomenon, AC responses to AVP were measured in medullary segments of the thick ascending limb of Henle’s loop (MAL) and the collecting tubule (MCT), microdissected from DI and control rats of the same strain. AVP dose-response curves determined in MCT from DI and control rats were identical, indicating that, in that nephron segment, the enzyme response to the hormone was normal in DI rats. In contrast, AC activities measured simultaneously in MAL were on the average 50% lower (p, < 0.001) in DI than in control rats for all AVP concentrations tested. The apparent affinity constant of enzyme activation by the hormone was similar in both groups of animals. These results suggest that the concentrating defect of DI rats in the presence of AVP could result from a subnormal AC responsiveness to AVP selectively affecting MA

ISSN:1420-4096    

DOI:10.1159/000172639

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Systemic and renal hemodynamics, and plasma antinatriferic activity (AA) were measured before, during 2 h of saline loading, and for 1 h immediately after stopping saline infusion in dogs. During loading, mean arterial pressure (MAP), central venous pressure (CVP), renal blood flow (RBF), glomerular filtration rate (GFR), and AA increased as sodium excretion as (UNaV) rose progressively. During the post-loading period, MAP, CVP, and AA returned to baseline, RBF and GFR remained elevated, while UNaV fell. Only 52 ± 3% of the total sodium load was excreted during the study. These data show that AA is not regulated by the absolute volume of extracellular fluid. The correlation of AA with changes in systemic hemodynamics suggests ‘volume receptors’ in the resistance and/or capacitance circulation. The data suggest that the post-loading fall in UNaV is due at least in part to decreased levels of a humoral natriuretic fa

ISSN:1420-4096    

DOI:10.1159/000172640

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Renal absorption of calcium and magnesium occurs in the proximal tubule, and at unknown site(s) beyond this segment. In the presence of blockade of Henle’s loop by ethacrynic acid, the excretion of calcium, magnesium and sodium in response to acetazolamide as compared to that with parathyroid hormone (PTH) was examined. Addition of acetazolamide to ethacrynic acid increased calcium and sodium excretion, but did not change magnesium excretion. In contrast, PTH added to ethacrynic acid did not change the excretion of any of the ions under investigation. Analysis of calcium and magnesium excretion as a function of sodium excretion, however, suggests that ethacrynic acid inhibited the effect of PTH to augment calcium absorption, but did not alter magnesium absorption, implying that the nephron site of PTH action to augment calcium absorption is the ascending limb of Henle’s loop and that to augment magnesium absorption resides beyond Henle’s

ISSN:1420-4096    

DOI:10.1159/000172641

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Sodium and bicarbonate reabsorption was measured in proximal tubules of remnant kidneys of rats with secondary hyperparathyroidism (NX rats). In 7 of 15 NX rats, parathyroidectomy (PTX) was carried out 1 h before starting micropuncture study (NX-PTX rats). Bicarbonate reabsorption was measured over a range of plasma HCO-3 concentrations from 20 to 60 mEq/1. TF/Phcct3 was significantly lower in NX and NX-PTX than in control rats, and proximal HCO-3 reabsorption was higher. PTX did not significantly alter proximal sodium or HCO-3 reabsorption. In contrast, acute PTX decreased fractional excretion of Na+, HCO-3, and H20 in the final urine. These findings suggest that PTH may inhibit electrolyte and water reabsorption beyond the proximal tubule in the kidney with a reduced nephron mass.

ISSN:1420-4096    

DOI:10.1159/000172642

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Pregnant rats became significantly heavier than non-pregnant controls 2 days after conception. Just prior to term, they exhibited a gross 52% increase over their non-pregnant body weight. Dry kidney weight had increased by 13% in 7-day-pregnant animals, which also showed a 20% increase in proximal renal tubule lengths. At term, the former was not maintained as compared with controls; whereas the latter is maintained throughout pregnancy, and may, at least partially, account for the enhanced renal reabsorption of salt and water found in these animals.

ISSN:1420-4096    

DOI:10.1159/000172643

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

An oversulfated dermatan sulfate (DS) was isolated from bovine and human kidney glycosaminoglycans by elution at high NaCl concentrations through ion-exchange column chromatography. Based on its behavior on paper chromatography and electrophoresis after digestion with chondroitinases, the presence of an oversulfated DS was evidenced by detection of the umsaturated disulfated disaccharide unit. Judging from its susceptibility to chondrosulfatases, it was found that the oversulfated DS comprised mainly the disaccharide unit of iduronosyl-N-acetyl-D-galactosamine 4- and 6-sulfates. A possible function of the oversulfated DS in kidney tissue is discussed.

ISSN:1420-4096    

DOI:10.1159/000172644

出版商:S. Karger AG    

年代:1978

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000172645

出版商:S. Karger AG    

年代:1978

数据来源: Karger