Vitamin A and Lysosomal Stability in Rat Liver

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Abstract
The stability of rat liver lysosomes has been studied in animals of varying vitamin A status. The activities of various hydrolytic enzymes—β-glucuronidase, β-hexosaminidase, hyaluronidase, cathepsins and arylsulfatase—in the lysosome-rich 15,000 g sediment and the 15,000 g supernatant and in the serum have been taken as criteria of lysosomal stability. Maximum lysosomal stability has been found in rats when the vitamin A intake ranged from 100 to 2,000 IU/day. Within this range the variation in lysosomal stability was not appreciable, but above and below this range of vitamin A intake, the stability was progressively decreased. There was no appreciable alteration in the total enzyme activity (sum of the nuclear, bound, and free activities) with variations in vitamin A status. Retinol in vitro had no effect on the enzyme activity released from the nuclear or lysosomal fraction by the action of Brij-35 or on the nonsedimentable activity. The action of vitamin A is therefore mainly a membrane effect. Proteoglycan fraction from normal rat liver had no effect on the lysosomal stability of the vitamin A-deficient rat in vitro, but lipid extract from normal rat liver increased the stability. This effect has been found to be due to the phospholipids present in the lipid extract.