RESUMEN
The effect of the phenothiazines, thioridazine and chlorpromazine, on the increased hepatic NAD+ level of rats fed clofibrate, a hypolipidaemic drug, has been investigated. Short-term (6 days) addition of phenothiazines to the diet negatively affected diet intake and body-weight gain, but increased liver weight and hepatic NAD+ levels, which was synergistic to clofibrate. The phenothiazines were shown to inhibit hepatic peroxisomal fatty acid oxidation in-vivo, as determined by the increased residual catalase activity. In hepatocytes prepared from clofibrate-fed rats, phenothiazines inhibited not only peroxisomal but also mitochondrial fatty acid oxidation to the same extent. In the hepatocytes, NAD+ was maintained at the high level until the phenothiazine concentration was increased to 0.2 mM. The result suggests that the increase of hepatic NAD+ in rats fed clofibrate is not related to peroxisomal fatty acid oxidation.