DIFFERENTIAL EXPRESSION PATTERN OF RETINOID-X-RECEPTORS IN ADULT MURINE TESTICULAR CELLS IMPLIES VARYING ROLES FOR THESE RECEPTORS IN SPERMATOGENESIS

Retinoids have previously been shown to be crucial for normal spermato genesis. The role of retinoic acid receptors has been studied, but rel atively little is known about the function of retinoid X receptors (RX Rs). To gain more insight in the function of RXRs during spermatogenes is, the cellular localization of RXRs in the mouse testis was examined using immunohistochemistry and RNase protection assays. In both norma l and vitamin A-deficient (VAD) testes, a strong immune response to an RXR alpha antibody occurred in Leydig cells, peritubular myoid cells, and A spermatogonia. Weaker signals were found in spermatocytes and s permatids. In normal testes, an RXR beta antibody gave a reaction in L eydig cells, and, to a lesser extent, in Sertoli cells, A spermatogoni a, pachytene spermatocytes, and spermatids. In Leydig cells, a cytopla smatic signal was found in addition to the nuclear signal. in the VAD testis, only Leydig cells and A spermatogonia were positive, which ind icates that RXR beta expression may be dependent on the retinoid statu s. Previous studies have shown RXR gamma mRNA expression in the mouse testis at a low level. Nevertheless, an RXR gamma antibody caused a st rong immune response in interstitial cells and in A spermatogonia, and a weak signal in pachytene spermatocytes. These immunohistochemical d ata were supported by the results of RNase protection assays on mRNA o f testicular cell isolations. In conclusion, the different RXRs in the mouse testis have distinct expression patterns, suggesting that they may have different functions.