Department of Biochemistry¡ Biophysics, Washington State University, Pullman, Washington 99164-4660 Received April 16, 1987; Revised Manuscript Received June 12, 1987 abstract: When cultured Sertoli cells derived from 20-day-old weanling rats were supplied [3H] retinol bound to serum retinol binding protein-transthyretin complex,[3H] retinol was rapidly incorporated and [3H] retinyl esters were synthesized. Within 28 h after administration, 83% of the labeled retinoids were accounted for as retinyl esters (64% as retinyl palmitate). Sertoli cells derived from vitamin A deficient rats and supplied [3H] retinol in culture under identical conditions likewise incorporated [3H] retinol and synthesized retinyl esters. In contrast to normal Sertoli cells, vitamin A deficient Sertoli cells eventually metabolized virtually all of the cellular [3H] retinol to retinyl esters. The primary metabolic fate of retinol administered to Sertoli cell cultures was the synthesis of retinyl esters under all conditions tested. However, administration of [3H] retinol boundto serum retinol binding protein gave metabolic profiles having a higher proportion of retinyl esters andlower proportions of unresolved polarmaterial than administration of [3H] retinol alone. The kinetics of retinol uptake and intracellular retinyl ester synthesis in cultured Sertoli cells was complex. An initial, rapid phase of [3H] retinolincorporation lasting 30 min was followed by a slower rate of incorporation and a concomitant decrease in the intracellular concentration of [3H] retinol. During the time course the specific activity of [3H] retinyl palmitate eventually exceeded that of intracellular [3H] retinol. These observations suggest that two intracellular pools of retinolmay exist in Sertoli cells.