The in vitro effects of vitamin D on oxidative phosphorylation and adenosine triphosphatase activity by rat liver mitochondria

Abstract

Ergocalciferol (vitamin D 2 ) and cholecalciferol (vitamin D 3 ) were found to depress ATP synthesis, state 3 and 2,4-dinitrophenol-stimulated respiration of rat liver mitochondria. This action of the D vitamins is not antagonized by the addition of excess dithiothreitol. The degree of inhibition on mitochondrial oxidative phosphorylation is greater when the mitochondria are respiring in the presence of NAD-linked substrates than with succinate. Vitamin D does not inhibit the mitochondrial ATPase (ATP phosphohydrolase. EC 3.6.1.4) activity induced by 2,4-dinitrophenol; however, in the absence of the uncoupler, vitamin D was found to significantly stimulate this mitochondrial enzyme. The vitamin D-stimulated ATPase activity is inhibited by oligomycin. Dihydrotachysterol 2 has little or no effect on mitochondrial oxidative phosphorylation and ATPase activity. The sites of action of vitamin D on the energy transfer pathway of rat liver mitochondria and the possible implications of these observations with regard to the biological actions of vitamin D are discussed. © 1975.