Dual effects of calcium on the oxidation of fatty acids to ketone bodies in liver mitochondria.

The addition of calcium ions (Ca2+) to rat liver mitochondria, under conditions of rapid accumulation of 10-40 nmol Ca2+/mg protein, inhibited the oxidation of long and medium chain fatty acids to ketone bodies, whereas higher quantities of Ca2+ activated the process. The mitochondrial NADH:NAD ratio exhibited corresponding depression and elevation. Both inhibitory and stimulatory actions of Ca2+ were operative in liver mitochondria from fed and fasted rats and appear to be localized in the mitochondrial inner membrane-matrix region. These observations may signify involvement of Ca2+ in the regulation of fatty acid oxidation and ketogenesis.