STAGE AND CELL-SPECIFIC EXPRESSION OF THE ADENOSINE 3',5'-MONOPHOSPHATE-PHOSPHODIESTERASE GENES IN THE RAT SEMINIFEROUS EPITHELIUM

Four genes (ratPDE1/IVc, ratPDE2/IVa, ratPDE3/IVd, and ratPDE4/IVb) en coding different isoforms of phosphodiesterase that specifically hydro lyze the second messenger cAMP (cAMP-PDEs) are present in the rat. Pre vious data from our laboratory indicated that these genes are differen tially expressed in the somatic and germ cells of the seminiferous epi thelium of the testis. To further characterize their spatial and tempo ral expression in the seminiferous tubules, in situ hybridization was used to monitor the expression of the four cAMP-PDE messenger RNAs (mR NAs). The signals corresponding to ratPDE1/IVc and ratPDE2IVa mRNAs we re localized in two restricted layers of the seminiferous epithelium. The ratPDE1/IVc mRNA was present in a region of the epithelium corresp onding to the location of middle-late pachytene spermatocytes. Convers ely, the ratPDE2/IVa signal was confined to a more adluminal area corr esponding to the location of maturing round spermatids. The ratPDE3/IV d ratPDE4/IVb mRNAs were distributed throughout the span of the semini ferous epithelium, indicating a localization in the Sertoli cell cytop lasm. Although the intensity of the signal corresponding to ratPDE4/IV b was similar in all seminiferous tubule stages, the ratPDE3/IVd signa l varied in intensity in tubules at different stages of the seminifero us cycle. Maximal expression was present in tubules at stages I-V and XI-XIII of the cycle and minimal at stages VIII-IX of the cycle. The e xpression of the ratPDE3/IVd mRNA positively correlated with the abili ty of specific inhibitors of the cAMP-PDEs to potentiate the FSH-depen dent cAMP accumulation in tubules at different stages of the seminifer ous cycle, with maximal potentiation observed at stages II-VI of the c ycle. These data demonstrate that different cAMP-PDE genes are active in different cells of the seminiferous tubules and that the ratPDE3/IV d gene is expressed in the Sertoli cell in a cyclical fashion during t he seminiferous cycle.