No abstract

In order to understand the physiological importance and molecular mechanisms of retinoic acid regulation of spermatogenesis, we examined the ontogeny of the steady-state level of the mRNAs of retinoic acid receptor (RAR) alpha and gamma in testes; we also used Northern blot cDNA hybridization to examine the distribution of RAR alpha and RAR gamma in spermatogenic cells isolated from 60-day-old rats. In addition, we investigated the effects of exogenous testosterone on the steady-state levels of mRNA of RAR alpha and gamma in testes of 20-day-old rats. The steady-state levels of both the 3.4- and 2.7-kb mRNA transcripts of RAR alpha in rat testes remained relatively unchanged until 20-21 days of age, then declined thereafter. Comparison of the relative abundance of the RAR alpha transcripts in Sertoli cells isolated from 20-day-old rats with that found in mixed spermatogenic cells isolated from 40-day-old rats suggests that both the 3.4- and the 2.7-kb transcripts were expressed more abundantly in Sertoli cells. Whereas young and pachytene spermatocytes, as well as young and elongated spermatids, all contained the 3.4-kb transcript of RAR alpha, only trace amounts of the 2.7-kb transcript was detected in spermatogenic cells. In addition, trace amounts of a smaller transcript of RAR alpha (1.8 kb) was detected in both Sertoli cells and spermatogenic cells, and two larger transcripts (4.0 and 7.0 kb) were detected exclusively in spermatogenic cells. In contrast, a single 3.4-kb mRNA transcript of RAR gamma was detected in rat testes.(ABSTRACT TRUNCATED AT 250 WORDS)