title: Evidence for increased membrane permeability of plasmalemmal vesicles from livers of phenobarbital-induced CCl4-intoxicated rats.
abstract: We have observed a marked increase in Ca2+ permeability of plasma membranes isolated from rats treated in vivo with CCl4 (2 ml/kg), after phenobarbital induction and overnight fast. Regulation of intracellular free Ca2+ is vital to cell viability and function, and the increased plasma membrane permeability, if representative of a change occurring in vivo, may be a critical biochemical determinant of CCl4-induced hepatic necrosis. Permeability to small cations of liver plasma membrane vesicles of control and CCl4-dosed rats was tested by two independent methods: 1) Ca2+ efflux after passive loading in 1 mM Ca2+, and 2) 86Rb+ uptake driven by valinomycin-induced K+ diffusion potential after 100 mM KCl-equilibrated vesicles were stripped of external K+ by cation exchange. Both indicated markedly increased permeability in plasma membranes after CCl4 in vivo. First order rate constants of biphasic Ca2+ efflux were 0.272 and 0.0516 min-1 for controls and 1.78 and 0.171 min-1 for vesicles from CCl4-treated animals. 86Rb+ uptake by CCl4 vesicles was 47% of control. Total calcium contents of plasma membranes (prepared in the absence of EGTA) by atomic absorption were 17.4 +/- 2.0 (control) and 10.9 +/- 1.2 (CCl4) nmol/mg of protein (means +/- SE, p less than 0.025). In correlation with altered biochemical function, we found 4-fold increases in the content of 11-, 12-, and 15-hydroxyeicosatetraenoic acids in plasma membranes of CCl4-treated rats. Although these specific oxidized fatty acids are unlikely to be ionophores, the ionophoretic properties of certain other oxygenated polyunsaturated fatty acids suggest a mechanism whereby accumulation of lipid oxidation products may be responsible for the altered membrane permeability we have observed after CCl4, and perhaps ultimately for cell death in CCl4-induced hepatic necrosis.
mesh_terms: D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002251:Carbon Tetrachloride / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects*; D002463:Cell Membrane Permeability / Q000187:drug effects*; D004533:Egtazic Acid / Q000494:pharmacology; D008099:Liver / Q000187:drug effects*; D008297:Male; D017830:Octoxynol; D010634:Phenobarbital / Q000494:pharmacology*; D011092:Polyethylene Glycols / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D000001:Calcimycin; D011092:Polyethylene Glycols; D004533:Egtazic Acid; D017830:Octoxynol; D002251:Carbon Tetrachloride; D011188:Potassium; D002118:Calcium; D010634:Phenobarbital