Sertoli cells secrete both testis-specific and serum proteins.

Abstract

The secretions of the Sertoli cell were examined with 2 polyvalent antisera: 1 prepared against proteins in rat serum and the other against testis-specific proteins in rete testis fluid. These antisera detected 12 serum and 9 testis-specific proteins in rete testis fluid. To determine the origin of these proteins, primary cutures enriched in Sertoli cells were incubated with [35S]methionine, and the radiolabeled proteins in the medium were immunoprecipitated. Gel electrophoresis of the 2 immunoprecipitates resolved 8 serum and 9 testis-specific proteins. These 2 sets of proteins were specifically bound by their respective antiserum and were immunologically distinct. Medium from Sertoli cell cultures contained 10 times more of the testis-specific proteins than did cultures enriched for testicular myoid or interstitial cells. The concentration of the serum proteins in Sertoli cell medium was 5 and 10 times greater, respectively, than in myoid or interstitial cell preparations. The proteins from Sertoli cells were next characterized on 2-dimensional gels. Seven of the proteins recognized by antiserum against serum proteins had identical MW and isoelectric points as serum proteins. Three of these proteins were ceruloplasmin, transferrin and glycoprotein 2. In addition to the proteins immunoprecipitated by the 2 antisera, > 60 other proteins were detected on 2-dimensional gels of the total secretory proteins. The Sertoli cell secretes many proteins, some of which are specific to the testis and others of which are similar to serum proteins.