VITAMIN-A CONTAINED IN THE LIPID DROPLETS OF RAT-LIVER STELLATE CELLSIS SUBSTRATE FOR ACID RETINYL ESTER HYDROLASE

Vitamin A is stored in the lipid droplets of liver stellate cells (LSC s), as retinyl esters whose hydrolysis is necessary for the secretion of retinol into the blood. Here, we isolated these retinyl esters unde r their physiological form, i.e., in LSC lipid droplets, which had ret ained their morphological and biochemical characteristics. These retin yl esters are substrate for an hydrolytic enzyme, whose optimum pH is 4.1, and which is kinetically similar to the acidic retinyl ester hydr olase (3REH) we had previously described (Mercier et al., Biochim. Bio phys. Acta (1994) 1212, 176-182). The cellular and subcellular localiz ations of aREH activity in rat liver suggest that this enzyme could be involved in the hydrolysis of the esterified vitamin A stores.