Studies on polypeptide composition, hydrolytic activity and proton conduction of mitochondrial F0F1H+ATPase in regenerating rat liver

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Abstract
A study of the F0F1 ATPase complex of mitochondria isolated from regenerating rat liver following partial (70%) hepatectomy is presented. As we have previously reported, ATPase activity in submitochondrial particles prepared from regenerating rat liver 24 h following partial hepatectomy was depressed by 75% with respect to controls (submitochondrial particles from sham‐operated animals). Polyacrylamide gel electrophoresis and immunodecoration using an antibody raised against isolated bovine heart F1 sector of the F0F1 ATPase indicated a substantial decrease in F1 content in the mitochondrial membrane from regenerating rat liver. Proton conduction by the F0F1 ATPase complex was studied by following the anaerobic relaxation of the transmembrane proton gradient (ΔμH+) generated by succinate‐driven respiration. In control rat‐liver submitochondrial particles containing the F0F1 moiety of the ATPase complex, anaerobic relaxation of ΔμH+ showed biphasic kinetics, whilst the same process in particles derived from regenerating rat liver exhibited monophasic kinetics and was significantly more rapid. Oligomycin and N,N‐dicyclohexyl carbodiimide [(cHxN)2C] inhibited proton conductance by the F1‐F0 ATPase complex in submitochondrial particles from both control and regenerating rat liver. Binding of [14C](cHxN)2C and immunodecoration using an antibody raised against bovine heart oligomycin‐sensitivity‐conferring protein (OSCP) indicated no difference in the content of either the (cHxN)2C binding protein or OSCP between control and regenerating rat‐liver mitochondrial membranes. The results reported show that the structural and functional integrity of the F0‐F1 ATPase of rat liver is severely perturbed during regeneration.