摘要:

Metabolism of very low density lipoprotein-triglyceride (VLDL-TG) was studied in the isolated perfused rat kidney (IPRK). Recirculating perfusate consisted of KrebsHenseleit bicarbonate buffer containing 6% defatted albumin and VLDL-TG which has been labelled in vitro with 14C-tripalmitin. Results show that the IPRK catabolizes VLDL-TG. Renal removal of VLDL-TG from perfusate was impaired in the presence of 1.0 mM palmitate. A lower palmitate concentration, 0.4 mM, was without effect. It is concluded that high concentrations of circulating free fatty acids impair renal metabolism of fatty acids derived from VLDL-TG.

ISSN:1420-4096    

DOI:10.1159/000173028

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The normal filtered load of albumin at the rat glomerulus was estimated to be 18 mg/24 h × g kidney weight by means of micropuncture studies. Total nephron fractional reabsorption was 91%. The proximal convoluted tubule accounted for 72% of total reabsorption followed by an additional 12% in the loop of Henle. Only minimal protein uptake occurred in more distal parts of the nephron. Na maleate, given at a dosage of 2 mM/kg body weight 2 h prior to micropuncture, inhibited tubular albumin uptake in the proximal convoluted tubule. As in controls there was no measurable protein uptake beyond the loop of Henle. These results indicated that tubular reabsorption of albumin was virtually completed by the early distal convoluted tubule. Maleate was found to be a potent inhibitor of protein transport in the proximal convoluted tubule resulting in a fractional excretion of albumin of 50%

ISSN:1420-4096    

DOI:10.1159/000173029

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The phosphorylation of rat renal brush border membrane protein was analyzed after incubation of cortical slices with 32P-orthophosphate and compared with the phosphorylation by γ-32P-ATP of isolated brush border vesicles. Phosphate incorporation into brush border membranes isolated from slices was linearly related to the incubation time as well as to the specific activity of orthophosphate present during slice incubation. Incorporation of phosphate into proteins reached an equilibrium after about 60min, whereas incorporation of phosphate into lipids increased continuously. In brush border membranes isolated from slices incubated with orthophosphate (32P), the addition of cAMP or theophylline produced a dephosphorylation of a 47,000-dalton protein; no increased phosphorylation was observed. In brush border membranes, phosphorylated with γ-32P-ATP, cAMP and dibutyryl cAMP (dB-cAMP) produced an increase in phosphorylation but no dephosphorylation. Sodium-dependent phosphate transport in brush border membranes was not altered by an incubation of slices with cAMP or dB-cAMP. These observations suggest that the phosphorylation machinery of isolated rat renal brush border membranes does not correspond with the mechanisms leading to phosphate incorporation into brush border membrane proteins in the intact cel

ISSN:1420-4096    

DOI:10.1159/000173030

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The effect of phosphate infusion on renal tubular handling of calcium and phosphate was examined in dogs which had been thyroparathyroidectomized (TPTX) immediately prior to the studies. Phosphate infusions in TPTX animals caused a small decrease in total and ultrafilterable plasma calcium, and decreased phosphate reabsorptive capacity in the proximal tubule and loop segment. Infusion of CaCl2 during phosphate loading to offset the fall in plasma calcium prevented the reduction in proximal phosphate reabsorptive capacity. However, between the proximal and distal sampling site, the reduction in phosphate reabsorptive capacity could not be prevented by CaCl2 administration. These data are consistent with the presence of two phosphate transport systems; one in the early proximal tubule, modulated by changes in plasma calcium level, and a second in the loop segment, which is independent of calcium. While the data suggest that the depression of proximal phosphate reabsorption during phosphate infusion may be secondary to the fall in plasma calcium concentration, they do not exclude a direct effect of infused phosphate on proximal phosphate reabsorption that may be antagonized by an opposing direct effect of the calcium infusion.

ISSN:1420-4096    

DOI:10.1159/000173031

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The portion of Na-K-ATPase activity on oxygen consumption was determined in suspensions of rat proximal tubules by monitoring oxygen consumption (QO2) under different metabolic states: in the presence or absence of succinate or lactate (10 mmol/l) and increasing concentrations of ouabain (0.4; 0.8; 1.2 and 1.6 mmol/l). In the metabolic states tested, the ouabain induced decrease of QO2 was identical, which implies a fixed rate between Na-K-ATPase activity and QO2. On the basis of these results, Ki and maximal inhibition rate were determined by Lineweaver-Burk and Eadie-Hofstee plots. Ki was 0.67 mmol/l ouabain and the maximal inhibition of QO2 was 77%. This corresponds to an absolute decrease of QO2 of 1,630 µmol O2 h-1 g-1 protein. Since this value represents the real portion of Na-K-ATPase on QO2, the activity of Na-K-ATPase can be calculated, yielding an activity of 163 µmol ATP min-1 g-1 tubule protei

ISSN:1420-4096    

DOI:10.1159/000173032

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

A simple, sensitive, and efficient method is described for the quantitative determination of glycosaminoglycans from bovine renal glomerular basement membranes. After release from glomerular basement membrane by protease treatment, the glycosaminoglycans were isolated by a modified DEAE-cellulose column chromatographic procedure. Quantitation of glycosaminoglycans was achieved by hexuronate measurements with a microadaptation method employing m-hydroxydiphenyl. This procedure has proven useful in analyzing small samples of basement membranes as little as 0.75 mg. The glycosaminoglycan was identified as heparan sulfate by cellulose acetate electrophoresis and nitrous acid treatment.

ISSN:1420-4096    

DOI:10.1159/000173033

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The histochemical activities of nonspecific acid and alkaline phosphatases, NADH- and NADPH-tetrazolium reductases, α-glycerophosphate dehydrogenase, succinate dehydrogenase, isocitrate dehydrogenase, lactate dehydrogenase and glucose-6-phosphate dehydrogenase were investigated in kidneys from rats treated with lithium and lithium plus neuroleptics. During the first 8 weeks of lithium treatment the activity of NADH-tetrazolium reductase, succinate dehydrogenase and α-glycerophosphate dehydrogenase activity in the collecting ducts increased. The other enzymes did not change. After 8 weeks of treatment no further changes in enzyme activity occurred. Withdrawal of lithium caused normalization of enzyme activity after 8 weeks. A decrease in concentration ability was found in parallel with the increase in enzyme activities (p < 0.001). The changes in enzyme activity were not significantly correlated to morphological changes in the collecting ducts. Treatment with neuroleptics alone caused no change in enzyme activity. During combined lithium plus neuroleptic treatment the enzyme activities changed in a similar way as during lithium therapy, but the changes were less pronounced. In parallel, a less pronounced decrease in concentration ability was found during this treatmen

ISSN:1420-4096    

DOI:10.1159/000173034

出版商:S. Karger AG    

年代:1985

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000173035

出版商:S. Karger AG    

年代:1985

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000173036

出版商:S. Karger AG    

年代:1985

数据来源: Karger