摘要:

Rat kidneys were perfused with a cell-free perfusate containing substrate-free albumin, different glucose concentrations (0.20–5.0 mmol/l), and uniformly labeled 14C-glucose. The rate of glucose decarboxylation (Qox), as a function of [glucose]p, displayed saturation kinetics [Vmax = 0.35 µmol/(g · min); Km = 0.87mmol/l]; saturation occurred at [glucose]p = 1.0–2.0mmol/l. Although the presence of as low as 0.2mmol/l of glucose significantly increased fractional sodium reabsorption (%TNa), there was no correlation between [glucose]p or Qox and %TNa. However, free water clearance (CH2O or CH2O/GFR) was directly proportional to [glucose]p and independent of Qox. We conclude that (1) in the absence of other substrates, renal glucose Qox saturates at hypoglycemic levels of glucose and (2) glucose plays an important role in the generation of solute-free water, a role that is unrelated to glucose Qox<

ISSN:1420-4096    

DOI:10.1159/000173391

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

Kidneys of normal female and male Wistar-Kyoto rats were studied by standard morphological techniques and morphometry in order to evaluate possible differences in the overall kidney morphology between both sexes. Furthermore, we investigated the role of testosterone (DHT) on kidney morphology by treating females with daily DHT injections. Kidney weight and volume in relation to body weight were not significantly different between males and females and were not affected by DHT. Differences were found in the volume distribution among the kidney zones. The cortex was larger in males than in females, whereas the medulla was conspicuously larger in females than in males. The greater volume of the cortex in males was mainly due to a more extensive development of proximal tubules. DHT treatment in females increased the volume of their proximal tubules. Glomerular volume was similar among the three groups. Within the medulla, the difference was most prominent in the inner stripe (14.9% of the total kidney volume in females vs. 8.9% in males) and was also important in the inner medulla (7.0 vs. 4.8%). The absolute epithelial volume of thick ascending limbs in this zone was larger in females than in males. This difference was more pronounced in short loops (≈20%) than in long loops (≈10%). The values of the DHT-treated females ranged in between. In spite of the greater development of medulla and thick ascending limbs in females, urine concentration was higher in males than in females and maximum urinary concentrating ability after 48 h dehydration was not different between both se

ISSN:1420-4096    

DOI:10.1159/000173392

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

The immediate (1 day, D1) and late (90 days, D90) effects of unilateral nephrectomy on contralateral renal hemodynamics, and the renal handling of electrolytes and water were investigated in the whole animal. The immediate and late ability of the remnant kidney to autoregulate perfusate flow and glomerular filtration rate (GFR) was studied in the isolated perfused kidney of the rat. In the whole animal, in D1 rats as compared to controls, GFR calculated for a single kidney increased from 0.85 ± 0.3 to 1.1 ± 0.2ml/min (p < 0.05). In D90 rats GFR increased further and was similar to prenephrectomy GFR (1.4 ± 0.5 vs. 1.7 ± 0.5 ml/min, p NS). Urinary prostanoid excretion in 24 h, calculated for one kidney, increased by 50–500% in D1 rats, but returned to prenephrectomy values in D90 rats. In the isolated perfused kidney, decreasing perfusion pressure (PP) from 100 to 70mm Hg did not change the renal vascular resistance (RVR) in control and D90 kidneys, but in D1 kidneys RVR decreased from 8.6 ± 1.3 to 7 ± 1.3 mmHg/ml/min (p < 0.05). In D90 kidneys RVR was significantly lower as compared to control and D1 kidneys at all perfusion pressures. Decreasing PP from 100 to 70 mm Hg resulted in a significant decrease in perfusion flow in control, D1 and D90 kidneys, while with the increase in PP from 100 to 130 mm Hg the perfusion flow increased significantly in all three kidney groups. GFR was not influenced by the decrease in PP from 100 to 70 mm Hg in control and Dl kidneys, but in D90 kidneys GFR decreased from 532.7 ± 171.0 to 227.8 ± 70.0 µl/min (p < 0.01). In Dl kidneys, GFR was similar to that of controls at all perfusion pressures, while in D90 kidneys GFR was significantly higher than control or D1 kidneys at all perfusion pressures. These results indicate that: (a) the recovery in GFR observed at 90 days after uninephrectomy is not related to renal prostanoids; (b) the early increase in GFR is due to systemic factors (an increased GFR in Dl in the whole animal, and unchanged GFR in the isolated perfused kidney); (c) the late increase in GFR is due to both systemic and intrarenal factors (an increased GFR in D90 in both, whole animal and isolated perfused kidney); (d) control, D1 and D90 isolated perfused kidneys failed to autoregulate renal perfusate flow, however, control and D1 isolated kidneys autoregulated GFR when PP was lowered from 100 to 70 mm Hg, while D90 kidneys did not, and (e) the remarkable vasodilation found in D90 kidneys may potentially predispose these kidneys to pressure-rela

ISSN:1420-4096    

DOI:10.1159/000173393

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

We have examined the effects of endothelin (ET) on the renal microcirculation by in vivo microscopy using the model of the split hydronephrotic rat kidney. ET, a potent vasoconstrictor peptide synthesized by vascular endothehal cells, showed marked and long-lasting effects on glomerular blood flow and vessel diameters in various segments of the renal vascular bed. Intravenously applied ET (100 ng/min/kg) increased systemic blood pressure from 123 ± 7 to 156 ± 4 mm Hg, decreased glomerular blood flow by 70%, and preferentially constricted larger preglomerular vessels, e.g. the arcuate artery. The competitive leukotriene antagonist FPL55712 significantly attenuated the vascoconstrictor response of the larger vessels. Local ET adminstration decreased glomerular blood flow in a dose-dependent manner (50% reduction at a concentration of 2.6 ± 0.7 · 10-9M) and constricted smaller vessel segments, e.g. the afferent and efferent arterioles near the glomerulus. The constriction induced by ET was not significantly affected by the Ca2+ channel blocker nitrendipine (2.8 · 10-6 to 1.1 · 10-5M). We conclude that intravenous ET effects are probably mediated by leukotrienes, inducing constriction of larger renal vessels. Locally administered ET acts directly on the renal vasculature, especially on smaller ve

ISSN:1420-4096    

DOI:10.1159/000173394

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

The aim of this study was to establish epithelial cell lines derived from defined nephron segments. Primary cultures were prepared from dissected proximal S2 segments of the rabbit kidney, and grown in monolayers. Immortalization was observed after nuclear microinjection of the cells with simian virus 40 DNA and resulted in the development of cell lines of epithelial morphology. These cell lines were maintained in culture for at least 24 passages, then cells were frozen. One of the cell lines, the RKPC-2, was selected and further characterized. RKPC-2 cells formed domes on impermeable supports, indicating fluid and solute transport. RKPC-2 cells formed continuous monolayers of low transepithelial resistance on collagen-coated filters. They were able to accumulate tetraethylammonium, an organic cation; however, no significant transcellular transport could be measured. We conclude that this cell line which shows characteristics of epithelial cells has maintained certain properties of intact proximal tubules, in particular the capacity to accumulate organic cations.

ISSN:1420-4096    

DOI:10.1159/000173395

出版商:S. Karger AG    

年代:1991

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000173396

出版商:S. Karger AG    

年代:1991

数据来源: Karger