Uptake and metabolism of retinol in isolated cells of germinal epithelium in vitro.

Retinyl esters were quantitatively the most significant product formed in short term incubations of isolated rat germinal cells administered 3H-retinol. 3H-retinyl palmitate was found to be the single most abundant metabolite accounting for approximately 80% of the total label 2 h after administration of 3H-retinol bound to bovine serum albumin. Differences were found in the relative activity of retinol uptake and metabolism between the various subpopulations of germinal cells separated by the staput sedimentation technique. The strongest correlation was between the magnitude of 3H-retinyl palmitate synthesis and the distribution of round spermatids. Large pachytene spermatocytes also appeared to correlate with 3H-retinyl palmitate synthesis although this correlation was ambiguous due to the presence of a small population of Sertoli cells and spermatogonia in these fractions. The concentration of cellular 3H-retinol was more than 10 fold greater in germinal cells administered 3H-retinol bound to bovine serum albumin than when 3H-retinol bound to serum retinol-binding protein was administered, and likewise the concentration of cellular 3H-retinyl palmitate was approximately 30 fold higher. In comparison to germinal cells, Sertoli cells administered 3H-retinol bound to serum retinol-binding protein incorporated 20 fold more 3H-retinol and synthesized more 3H-retinyl palmitate. However, both germinal cells and Sertoli cells were found to have incorporated similar concentrations of total label when administered 3H-retinol bound to bovine serum albumin. (ABSTRACT TRUNCATED AT 250 WORDS)