Peroxisomal fatty acid oxidation in rat and human tissues. Effect of nutritional state, clofibrate treatment and postnatal development in the rat.

Oxidation of palmitate 14C-labeled in different positions was assayed in the absence and presence of antimycin and rotenone in homogenates of various rat and human tissues to determine total and peroxisomal oxidation and acetyl group production. Total and antimycin-insensitive palmitate oxidation rates were higher in rat heart, liver and quadriceps muscle than in the corresponding human tissues. The proportion of antimycin-insensitive oxidation of [1-14C]palmitate was 17-35% in tissues of starved rats and in human muscles and fibroblasts, but peroxisomal production of acetyl groups amounted only to 5-11% of that by mitochondria. The mean number of peroxisomal beta-oxidation cycles was 1.5-2.5 per palmitate molecule. The nutritional state markedly influenced the total oxidation rate and the antimycin-insensitive proportion in rat liver. Clofibrate feeding increased total and antimycin-insensitive oxidation rates in liver, heart and kidney, but not in quadriceps muscle. Total oxidation capacity was maximal in rat liver at weaning, and in rat heart at an age of 70 days. Antimycin-insensitive oxidation rates increased in rat liver and heart at postnatal development up to weaning. A marked proportion of lignocerate oxidation was antimycin-sensitive in rat tissues.