No abstract

Isolated rat hepatocytes were exposed to hypotonic media (225 mosmol/l) for 5 and 15 min and processed for a quantitative electron microscopic stereologic analysis. Within 5 min of hypotonicity, the hepatocyte volume increased by 25% and thereafter displayed a volume regulatory decrease leading to mean cellular volume, which was 16% above that of controls. Stereologic analysis of the major subcellular compartment, the cytosol, showed an identical change as the whole cell. In contrast to that, the mitochondrial compartment increased in volume by 30% within the first 5 min of exposure and returned by regulatory volume decrease back to values of the isotonic controls after 15 min of hypotonicity. In contrast, hypotonicity (220 mosmol/l)-induced stimulation of flux through mitochondrial glutaminase and the glycine cleavage enzyme complex, as assessed by 14CO2 production from [1-14C]glutamine or [1-14C]glycine in isolated perfused rat liver persisted throughout a 15-min period of hypotonic exposure. Thus hypotonicity-induced alterations of mitochondrial metabolism apparently do not parallel the time course of mitochondrial volume changes. This suggests that persistent mitochondrial swelling is not required for functional alterations, but that the latter may be triggered by the initial swelling of mitochondria. Hypotonic exposure did not alter the nuclear volume of isolated hepatocytes. Cell membrane surface nearly doubled after 5 min of hypotonic exposure, but returned within 15 min of exposure to values observed in normotonic media. This may reflect the participation of exocytosis in hepatocyte volume regulation.

No abstract

To assess direct nephrotoxicity of Russell's viper venom (RVV; Daboia russelii siamensis), isolated rat kidneys were perfused in single pass for 120 min. Ten micrograms/ml and 100 micrograms/ml RVV were administered 60 minutes and 80 minutes, respectively, after starting the perfusion. Furthermore, cultured mesangial cells and renal epithelial LLC-PK1 and MDCK cells were exposed to RVV (100 to 1000 micrograms/ml) for 5 minutes up to 48 hours. The IPRK dose-dependently exhibited reductions of renal perfusate flow (RPF, 7.7 +/- 2.4 vs. 16.5 +/- 0.7 ml/min g kidney wt in controls, experimental values given are those determined 10 minutes after termination of 100 micrograms/ml RVV admixture), glomerular filtration rate (GFR 141 +/- 23 vs. 626 +/- 72 microliters/min g kidney wt) and absolute reabsorption of sodium (TNa 8 +/- 1.7 vs. 79 +/- 9 mumol/min g kidney wt), and an increased fractional excretion of sodium (FENa 60 +/- 7 vs. 8 +/- 0.8%) and water (FEH2O 68 +/- 3.2 vs. 13 +/- 1.2%). Urinary flow rate (UFR) showed both oliguric and polyuric phases. Functional alterations of this type are consistent with ARF. Light and electron microscopy of perfusion fixed IPRK revealed an extensive destruction of the glomerular filter and lysis of vascular walls. Various degrees of epithelial injury occurred in all tubular segments. In cell culture studies RVV induced a complete disintegration of confluent mesangial cell layers, beginning at concentrations of 200 micrograms/ml. In epithelial LLC-PK1 and MDCK cell cultures only extremely high doses of RVV (> 600 and 800 micrograms/ml, respectively) led to microscopically discernible damage. These results clearly demonstrate a direct dose dependent toxic effect of RVV on the IPRK, directed primarily against glomerular and vascular structures, and on cultured mesangial cells.