Unique adenosine 3',5' cyclic monophosphate phosphodiesterase messenger ribonucleic acids in rat spermatogenic cells: evidence for differential gene expression during spermatogenesis

Abstract

Four cAMP phosphodiesterase (cAMP-PDE) genes (ratPDE1, ratPDE2, ratPDE3, and ratPDE4) are expressed in the rat testis (Swinnen et al., PNAS USA 1989; 86:5325). Since multiple ratPDE1 and ratPDE2 mRNAs were present in male germ cells, their developmental expression was investigated by using purified spermatogenic cell populations. RatPDE1 mRNAs (4.0 and 2.8 kb) were found to be abundant in pachytene spermatocytes. RatPDE1 mRNA levels were decreased in round spermatids and absent from condensing spermatids/residual bodies. However, multiple ratPDE2 mRNAs (4.0, 3.5, 3.1, 2.8, and 2.4 kb) were abundant in round spermatids, and lower amounts were present in condensing spermatids/residual bodies. Transcripts related to ratPDE2 were also present in mouse round spermatids. Chromatography of germ cell cytosol identified two peaks of cAMP-PDE activity. Whereas peak A was evident in all germ cell populations examined, peak B was present in pachytene spermatocytes and round spermatids, but was at the limit of detection in condensing spermatids/residual bodies. The large decrease in peak B activity in condensing spermatids/residual bodies may be related to the drop in ratPDE1 mRNA levels observed during spermatogenesis. The sustained peak A activity in condensing spermatids/residual bodies coincides with the presence of ratPDE2 mRNA in these cells and suggests that the ratPDE2 enzyme may function during spermiogenesis and in spermatozoa.