CELLULAR LOCATION AND AGE-DEPENDENT CHANGES OF THE REGULATORY SUBUNITS OF CAMP-DEPENDENT PROTEIN-KINASE IN RAT TESTIS

This study was undertaken to examine the expression and cellular locat ion of the various cAMP-dependent protein kinase (PKA) subunits in dif ferent testicular cell types, using cDNA probes, isoenzyme-specific an tibodies and activity measurements. Amounts of mRNA and protein were e xamined in cultured Sertoli cells, cultured peritubular cells, germ ce lls (pachytene spermatocytes, round spermatids), Leydig cell tumours a s well as whole testes from rats of various ages. In Sertoli cells, th ere was a good correlation between the amount of mRNA and the respecti ve immunoreactive proteins. In other types of cell, such as germ cells and Leydig tumour cells, this was not always the case. Large amounts of RII(beta) mRNA were found in Leydig tumour cells, whereas the amoun t of immunoreactive protein was low. Furthermore, large amounts of sma ll-sized germ cell-specific mRNAs for RI(alpha) (1.7 kb) and RII(alpha ) (2.2 kb) were also found in the developing rat testis after 30 to 40 days of age, but the large amounts of mRNA were only partially reflec ted at the protein level. Pachytene spermatocytes and round spermatids were practically devoid of both RII(alpha) and RII(beta) protein. Dur ing spermatid differentiation, there was a decrease in RI(alpha) and a n increase in RII(alpha) protein. Cell specific distribution of the va rious PKA subunits in testicular cell types is described. In some type s of cell, discrepancies between mRNA and protein were demonstrated, w hich clearly suggest cell specific differences in translational effici encies for some of these mRNAs, particularly the small-sized mRNAs for RI(alpha) and RII(alpha) in meiotic and post-meiotic germ cells.