Vitamin A storage and peroxisomes in retinal pigment epithelium and liver

Retinas and livers were studied with histochemical methods for catalase combined with light and electron microscopy, following intramuscular injections of C57 black mice with retinyl acetate or retinyl palmitate in total doses of 0.9 to 6.7 X 10(6) I.U./kg. body weight. There were clear, dose-related increases in the numbers and sizes of vitamin A--storing lipid droplets in the stellate cells of the liver. Concomitantly, more conservative increases in similar lipid droplets occurred in the pigment epithelium but not in other cells of the retina. Such lipid droplets may represent physiological sites of vitamin A storage which are important for the maintenance of photoreceptor cells by the retinal pigment epithelium. No changes in lipids of the retina or liver were observed in mice injected with retinoic acid or with peanut oil. Both peroxisomes containing catalase and the putative vitamin A--storing lipid droplets were distributed along the basal and lateral cell surfaces of the pigment epithelium where receptors for plasma retinol-binding protein have been reported. Peroxisomes may play a role in the reactions related to the esterification and sequestering of vitamin A.