摘要:

Because the glomerular basement membrane (GBM) is subject to damage in a multitude of renal diseases, a model of basement membrane permeability properties would be useful for learning more about this important barrier. Isolated, perfused tubular basement membrane (TBM) allows measurement of permeability, but it is not known whether TBM is similar enough to GBM for data to be extrapolated from this model to the glomerulus. As a first approach to assessing differences between GBM and TBM, we looked at composition. Renal glomeruli and tubules were isolated from Swiss-Webster mice by sucrose-gradient centrifugation. GBM and TBM were isolated by sonication in 1% deoxycholate and then subjected to a sequential extraction procedure. Analysis of the solubilized basement membranes by electrophoresis revealed a complex mixture of proteins. Immunoblot analysis demonstrated that, among the proteins, laminin and fibronectin were found exclusively in the guanidine and guanidine/dithiotreitol extracts. The total amount of laminin extracted in GBM, 1.8+0.001 µg/mg dry weight (n = 2 groups animals, by inhibitory ELΙSA), was significantly less than in TBM, 3.4+0.1 µg/mg dry weight (n = 2); however, the total amount of fibronectin extracted did not differ between GBM and TBM, 8.2 ± 0.8 and 7.7 ± 1.0 µg/mg dry weight (n = 2) respectively. Examination of deoxycholate supernatants was carried out to see if components of GBM or TBM were solubilized during isolation of basement membranes. Immunoblot analysis revealed loss of some laminin and fibronectin occurred during the detergent isolation of GBM and TBM. We conclude that GBM and TBM are qualitatively similar in that they have the same protein components, but differ significantly in content of laminin and probably other macromolecular compo

ISSN:1420-4096    

DOI:10.1159/000173893

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Membrane-bound nucleotidases and phosphodiesterases are critical regulators of extracellular nucleic acid processing. We previously demonstrated that mesangial cell 5’-nucleotidase was an ectoenzyme, the expression of which was stimulated by macrophage-secreted products. We show in the present study that rat mesangial cell alkaline phosphodiesterase I is also an ectoenzyme characterized by a Km value of 0.41 mM and a Vmax of 20.8 nmol min-1 mg-1. Treatment of mesangial cells by dexamethasone increased alkaline phosphodiesterase I activity in a dose- and time-dependent manner. Maximal increase (×1.5) occurred after treatment with 1 µM dexamethasone for 5 days. Cycloheximide and RU 38486, a glucocorticoid receptor antagonist, suppressed the dexamethasone-induced increase in alkaline phosphodiesterase I activity. 5’-Nucleotidase activity was not modified by dexamethasone under similar conditions of study. In contrast with 5’-nucleotidase, alkaline phosphodiesterase I expression remained unchanged in the presence of macro-phage-conditioned medium or during cocultures of mesangial cells with macrophages. Interleukin-1, tumor necrosis factor, cyclic adenosine monophosphate and adenosine analogues also activated 5’-nucleotidase whereas they were inactive on alkaline phosphodiesterase I. These results suggest that extracellular DNA trapped in the mesangial area of the glomerular capillaries may be processed in part at the cell surface by alkaline phosphodiesterase 1 and that such an event may be regulated by glucocor-ticoids. They also show that alkaline phosphodiesterase I and 5’-nucleotidase obey a different

ISSN:1420-4096    

DOI:10.1159/000173894

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

The elevation in oxygen consumption (QO2) observed following addition of the sodium ionophore nystatin in suspensions of rabbit renal proximal tubules was significantly increased by 1 mM dibutyryl cyclic adenosine monophosphate (db-cAMP). The QO2 after subsequent addition of strophanthidin to block the sodium pump was unnaffected by db-cAMP. However, 10 µM forskolin in the presence of 100 µM IBMX had no significant effect on the QO2 observed following addition of either nystatin or strophanthidin. Nevertheless, we can conclude that db-cAMP does stimulate the sodium pump activity independently of sodium transport mechanisms in the rabbit renal proximal tubul

ISSN:1420-4096    

DOI:10.1159/000173895

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Rats with chronic partial unilateral ureteral obstruction (UUO) have a paradoxical resetting of the tubuloglomerular feedback (TGF) mechanism. During extracellular fluid volume expansion (VE) in control animals, a decrease in TGF sensitivity is normally noted. In rats with partial UUO, however, TGF sensitivity in the obstructed kidney was increased, associated with a relative reduction in single nephron glomerular filtration rate. In the present study, we examined the tubular and interstitial pressures, whole kidney function and the TGF system in rats with chronic partial bilateral ureteral obstruction. The rats were divided into preferentially ipsilaterally and preferentially contralaterally obstructed, as judged by pelvic volume. Measurements were performed both during hydropenia and during VE. During hydropenia TGF characteristics were the same in the 2 groups. During VE, however, TGF sensitivity was unchanged in the most obstructed kidneys (ipsilateral), while if the obstruction was preferentially contralateral, TGF sensitivity decreased. This opposite change in TGF sensitivity resulted in higher electrolyte and water excretion from the least obstructed kidney. The change in TGF sensitivity was not correlated to renal interstitial pressure. In conclusion: rats with moderate chronic partial bilateral ureteral obstruction have an almost preserved function with regard to renal hemodynamics and excretion during hydropenia. During volume expansion, however, different responses were found in the least and most obstructed kindeys, with a decreased sensitivity of TGF in the least obstructed kidney, while TGF sensitivity was unchanged in the most obstructed kidney.

ISSN:1420-4096    

DOI:10.1159/000173896

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

The diurnal time course of urinary flow rate (UV), urinary sodium (UNaV), and potassium (UKV) excretion, and of hormones such as atrial natriuretic peptide (ANP) and aldosterone, was investigated during 5 days of continuous captopril infusion (15 µg · kg body weigth-1 · min-1) in 4 conscious dogs on a high sodium diet (14.5 mmol Na·kg body weigth-1 24 h-1). All food and water was given once daily at 8.30 a.m. On the control day and on days 1, 3, and 5 of·captopril infusion, urine was collected by an automated system at 20-min intervals over 24 h, blood was taken every 4 h. Mean arterial blood pressure (MABP) and heart rate were evaluated as 5-min averages. Time courses of UNaV, UV, and UKV were compared with the individual control day without captopril. With captopril, 24-hour balances for Na and H20 were slightly negative, while the K balance was slightly positive for 2-3 days. Thereafter, all 24-hour balances were restored. MABP continued to decrease even after Na and water intake and output had come into balance again. Captopril treatment changed the diurnal excretion pattern for UNaV and UV characteristically. In the postprandial period until 5 p.m., less Na and urine were excreted than on the control day, whereas during the evening and night more Na and urine were excreted. The changes in the excretion pattern persisted for the entire observation period. The results indicate that disturbances in the regulating systems, induced by converting-enzyme blockade, bring about complex reactions of, e.g., MABP ANP and aldosterone that finally restore Na and water 24-hour input/output bala

ISSN:1420-4096    

DOI:10.1159/000173897

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

The machanisms that mediate the actions of bradykinin on ureteral motility are poorly defined and mediation via prostaglandins has not been examined. Therefore, the effects of bradykinin on contractility and the possible mediator role of prostaglandins have been investigated in sheep ureter. At the concentrations of 10-8, 10-7 and 10-6M, bradykinin elicited marked reductions in contractile force. When ureteral strips were treated separately with 10-6M indomethacín, 2x10-6M sodium salicylate and 10-5 M aspirin, each drug produced a significant decrease in contractile force. In strips in which prostaglandin synthesis was inhibited by the above concentrations of indomethacin, sodium salicylate and aspirin, 10-7M bradykinin significantly decreased the contractility. From these data, we concluded that in ureter bradykinin decreases contractility via a mechanism not involving prostaglandin generation

ISSN:1420-4096    

DOI:10.1159/000173898

出版商:S. Karger AG    

年代:1995

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000173899

出版商:S. Karger AG    

年代:1995

数据来源: Karger