부산대학교 도서관

Guanine nucleotide-binding proteins (G proteins) are key components in membrane signal transduction that may play an important role in testis function. The present study is the first description of cell-specific differences in the contents of G protein α-subunits and their mRNAs in isolated rat testicular cells (pachytene spermatocytes, round spermatids, Sertoli cells, peritubular cells). By using Western blot techniques Gi-3α was shown to be the only pertussis toxin (PTX) substrate present in all the testicular cells examined. Surprisingly, we observed a lack of immunoreactive Gi-1α/Gi-2α protein in pachytene spermatocytes and round spermatids in spite of significant levels of the corresponding mRNAs as revealed by Northern analysis. No immunoreactive Gsα was detected in germ cells, in agreement with previous findings that the hormone-sensitive adenylyl cyclase is absent in these cell types. Peritubular cells and Sertoli cells contained no Goα, whereas high levels of both immunoreactive protein and mRNA were found in pachytene spermatocytes. This indicates that the Goprotein may play a role at this stage of spermatogenesis. The stimulation of phospholipase C (PLC) in germ cell membranes by 5′-guanylyl imidophosphate indicates that PTX-sensitive PLC activation may be mediated by Goα or Gi-3α.