Retinyl palmitate, a major retinyl ester in rat testis seminiferous tubules. II. The Sertoli cell, site of retinol esterification.

The study was designed to 1) isolate and quantitate retinyl esters normally present in the testis seminiferous tubules (ST) and 2) determine whether the Sertoli (SE) cells in the ST have the enzyme system necessary to esterify retinol. In the first study testes from normal adult male rats were removed, the ST were isolated mechanically and retinol was extracted and separated into free and retinyl esters in a prestandardized alumina column. The fraction containing retinyl esters was hydrolyzed, and the fatty acid composition was determined gas chromatographically. The results showed that retinyl palmitate was the major retinyl ester in the testis ST constituting almost 55% of the total esters. In the second study adult male rats were given Busulfan (1,4, dimethylsulfonoxybutane) intraperitoneally twice six weeks apart. At the end of six weeks following injection, the testes from a few animals were examined histologically, and the results showed that Busulfan treatment destroyed the germinal epithelium completely but had no effect on the structural integrity of the SE cells. Labeled retinol (free) mixed in rat albumin solution was injected intratesticularly (in vivo study) or incubated (in vitro study) with ST which had been isolated from the testes of rats treated with Busulfan. The results of the studies indicate that labeled retinol (free) was converted to retinyl esters in the ST. Since the ratio of conversion of free retinol (labeled) to retinyl esters remained constant in the treated ST (which contained only Sertoli cells, the germinal epithelium having been destroyed) and in the control ST (which contained both Sertoli cells and germinal epithelium), we conclude that the Sertoli cells are the site of retinol esterification in the testis ST.