Clofibrate-induced increase in coenzyme A concentration in rat tissues

Abstract

1. When clofibrate [ethyl 2-(4-chlorophenoxy)-2-methylpropionate] was administered subcutaneously to rats (600mg/kg per day for 5 days), the concentration of CoA and its acyl derivatives increased in several tissues. The increase in total CoA was 3.2-fold in the liver, 1.8-fold in the kidney, 2.7-fold in the heart and 2.4-fold in skeletal muscle. 2. To study the mechanism of this phenomenon, clofibrate-treated rats were injected with [3H]pantothenate intracardially and killed after 15min, 30min, 1 and 2h and 1, 3, 5 and 7 days for the determination of the incorporation of radioactivity into CoA and its precursors. Incorporation into CoA after 2h was 6.2-fold in the liver as compared with the control values and 4.6-fold in the kidneys. 3. The disappearance of the label from CoA was very slow compared with the rate of incorporation; it exhibited exponential kinetics, and was slower in the livers of the clofibrate-treated rats (t½ 18.2 days) than in the controls (t½ 5.6 days). 4. The rate of CoA degradation, calculated from the calculated rate constants of the apparent first-order kinetics of the disappearance of the label and from the CoA pool sizes, was approximately the same in the clofibrate-treated animals (11.5pmol/min per g), and the controls (11.6pmol/min per g). 5. These rates of CoA degradation indicate that the effect of clofibrate on CoA concentration may be mainly due to inhibition of the enzymes of CoA degradation, although recycling of the label cannot be excluded. The increase in the rate of pantothenate incorporation into CoA suggests that clofibrate also increases the synthesis of CoA.