ISSN:1420-4096    

DOI:10.1159/000173202

出版商:S. Karger AG    

年代:1989

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000173203

出版商:S. Karger AG    

年代:1989

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000173204

出版商:S. Karger AG    

年代:1989

数据来源: Karger

摘要:

The activities of purine-metabolizing enzymes, 5’-nucleotidase, adenosine deaminase, and purine nucleoside phosphorylase in microdissected rat nephron segments were measured. The specific activity of 5’-nucleotidase was highest in the proximal tubules and the cortical collecting duct, but low in the glomerulus. In contrast, the highest activity of adenosine deaminase was found in the glomerulus. The distribution pattern of purine nucleoside phosphorylase was similar to that of adenosine deaminase. These results suggest that various nephron segments can form adenosine and that the glomerulus exhibits highest capacities to metabolize this nucleos

ISSN:1420-4096    

DOI:10.1159/000173205

出版商:S. Karger AG    

年代:1989

数据来源: Karger

摘要:

Recently, we demonstrated that an ATPase stimulated by K (and not inhibited by ouabain, Na-K-ATPase inhibitor) is present in the connecting tubule (CNT) and collecting duct segments of the rabbit. In this study, we determined the effects of high- and low-K diet on K-ATPase activity in the CNT and collecting duct segments of rabbit. One group of animals was given a low-K diet (34 mEq/kg diet) and the other group was given a high-K diet (700 mEq/kg diet) for 1 week. K-ATPase activity was measured by a microfluorometric assay in which ATP hydrolysis is coupled to oxidation of NADH. Low-K animals had plasma K = 3.1 ± 0.2 as compared with 5.5 ± 0.5 mEq/1 in high-K animals. Low-K animals had significant K-ATPase activity in CNT, CCD (cortical collecting duct) and MCD (medullary collecting duct). On the other hand, K-ATPase activity in all 3 segments from high-K animals was not significantly different from zero. These results support a hypothesis that chronic K loading suppresses the ouabain-insensitive K-ATPase in the distal nephro

ISSN:1420-4096    

DOI:10.1159/000173206

出版商:S. Karger AG    

年代:1989

数据来源: Karger

摘要:

Urea production from arginine was studied in vitro in the kidney of normal rats in tubule suspensions of the four different renal zones (cortex, outer and inner stripe of outer medulla, and inner medulla), and in individual microdissected nephron segments. Tissue was incubated with L-[guanido-14C]-arginine to measure cellular arginase activity. Addition of urease to the incubate freed 14CO2 from the 14C-urea formed by arginase and released from the cells. CO2 was trapped in KOH and counted. These experiments revealed that significant amounts of urea are produced in the outer stripe and in the inner medulla. This intrarenal urea generation takes place mainly in the proximal straight tubule and in the collecting duct, with increasing activity in these two structures from superficial to deep regions of the kidney. Urea is known to play a critical role in the urinary concentrating process. The fact that some urea can be produced in the mammalian kidney, and that the two structures showing this capacity are straight portions of the renal tubular system descending along the corticopapillary axis suggest that this urea production might play a role in the formation and/or maintenance of the medullary urea concentration gradient.

ISSN:1420-4096    

DOI:10.1159/000173207

出版商:S. Karger AG    

年代:1989

数据来源: Karger

摘要:

We recently observed a strong increase of 5’-nucleotidase in renal fibroblasts of rats that were anemic due to an immunity against erythropoietin. In order to test if the change of 5’-nucleotidase was related with anemia, we studied the distribution of the enzyme in irradiated rats treated with phenylhydrazine. The hematocrit of these rats decrased to 15% within 4 days and erythropoietin levels were more than 200 times over controls. After 7 days a histochemical study showed that the enzymatic activity and the immunoreactivity for 5’-nucleotidase was markedly enhanced in the fibroblasts of the cortical labyrinth. There was no modification of 5’-nucleotidase in other cell types of the kidney. The 5’-nucleotidase activity of renal fibroblasts in cell culture increased by 72% upon addition of 160 µM 5’-AMP to the culture medium for 8 days. We propose that anemia provokes an energy deficit in some structure in the cortical labyrinth. This might increase the concentration of 5’-AMP which would induce 5’-nucleotidase. An interesting consequence of these events would be an increased production of adenosine in the direct vicinity of some of its putative targets, the glomerular arterioles and the erythropoietin

ISSN:1420-4096    

DOI:10.1159/000173208

出版商:S. Karger AG    

年代:1989

数据来源: Karger

摘要:

Monoclonal antibody (MAb) against 11-hydroxysteroid dehydrogenase (11-HSD) has been raised by immunization of female balb/c mice. 11-HSD from solubilized rat renal microsomal protein could be bound in a modified ELISA using antimouse IgG and MAb against 11-HSD. On Western blots of solubilized rat renal microsomes the MAb recognized a single protein band of an approximate molecular weight of 35 kD. Immunohistochemical staining of rat renal tissue with the above MAb and the APAAP staining technique displayed a heterogenous reginal and subcellular distribution: glomeruli and arterioles were practically devoid of specific staining, as were epithelial cells in inner and outer medulla. Intense immunostaining was observed in PCT and particularly in PST, appearing granular with highest density around the nuclei. Here the enzyme bound to intracellular membranes may exert an autocrine function such as signal inactivation. In contrast to cortex, staining of interstitial cells was observed in renal medulla. The latter localization is compatible with the concept of a paracrine function of 11-HSD which might prevent corticosterone from gaining access to collecting duct cells.

ISSN:1420-4096    

DOI:10.1159/000173209

出版商:S. Karger AG    

年代:1989

数据来源: Karger

摘要:

Madin Darby canine kidney (MDCK) renal epithelial cell cultures have been investigated with respect to their potency to express carbonic anhydrase activity using histochemical methods. Acetazolamide inhibitable carbonic anhydrase activity could be detected in the cytoplasmic compartment as well as in the apical membrane of cells when grown on solid culture supports. Cells forming domes in MDCK monolayers exhibit the highest histochemically detectable enzyme activity. The attempt to subculture clonal cell lines from MDCK monolayer cultures resulted in the establishment of 5 clones, slightly different with respect to size and shape of cells and their potency to form domes. Scanning electron microscopy ensured the identification of one clone (1A4), which distinctly differed from the others with respect to the apical membrane architecture. Co-localization of peanut agglutinin and carbonic anhydrase activity at the plasma membrane always revealed a combined occurrence of enzyme reactivity and lectin binding in the apical membrane domain. Both, lectin binding and carbonic anhydrase activity were distinctly more intense in plasma membrane regions equipped with microvilli. From the results it is concluded that MDCK cells in tissue culture retained properties of intercalated cells of the nephron collecting duct segment.

ISSN:1420-4096    

DOI:10.1159/000173210

出版商:S. Karger AG    

年代:1989

数据来源: Karger

摘要:

The present study has been performed to test for cell volume regulatory potassium release from the isolated perfused rat kidney exposed to hypotonic perfusate and for its sensitivity to potassium channel blocker barium and calcium channel blocker verapamil. Replacement of 25 mmol/l NaCl with 50 mmol/l mannitol has little effect on effluent potassium activity, whereas subsequent omission of mannitol from the perfusate leads to a transient increase of effluent potassium activity, reflecting volume regulatory potassium release. Barium (1 mmol/l) leads to a marked transient decrease of effluent potassium activity, pointing to net cellular uptake of potassium. Verapamil (1 µmol/l) leads to a slight decrease of effluent potassium activity. Both barium and verapamil virtually abolish the rapid, transient increase of effluent potassium activity upon exposure to hypotonic perfusates. Thus, the substances either block or markedly retard volume regulatory potassium release. The apparent renal vascular resistance is transiently increased by exposure to hypotonic perfusates and by barium, but is reduced by verapamil. Cell volume regulation of isolated perfused mouse straight proximal tubules is retarded but not abolished by verapamil (0.1 mmol/l). In conclusion, cellular potassium release from rat kidney can be determined by continuous measurement of effluent potassium activity. The volume regulatory potassium release and cell volume regulation are impaired by both barium and verapamil. The persisting cell volume regulation could be due either to slow potassium release and/or some mechanism independent of potassium

ISSN:1420-4096    

DOI:10.1159/000173211

出版商:S. Karger AG    

年代:1989

数据来源: Karger