A GERM-CELL FACTOR(S) MODULATES PREPROENKEPHALIN GENE-EXPRESSION IN RAT SERTOLI CELLS

Within the seminiferous tubule, both Sertoli and specific germ cells express opioid genes. Little is known about the paracrine regulation or role of opioid gene expression in the tubule. The present study shows that interactions among cells within the tubule may play a role in regulating preproenkephalin (PPenk) gene expression. Rat pachytene spermatocytes (PS) and round spermatids (RSd) were purified by centrifugal elutriation and established as primary cultures or co-cultured with Sertoli cells. The effects of germ cells or germ cell-conditioned media were studied to determine the expression of one of the opioid precursor genes in rat Sertoli cells, the PPenk gene. Following a 24 h co-culture with either PS or RSd, the expression of PPenk gene in Sertoli cells was increased 6.4- and 1.9-fold, respectively. Conditioned media obtained from either PS or RSd cultured for 20 h stimulated PPenk mRNA levels in Sertoli cells from as early as 2 h after exposure; maximum increases of 3.5- and 7.6-fold were observed at 12 h, respectively. The molecular weight of the germ cell factor(s) is greater than 30 kDa. 2 h after the addition of either PS- or RSd-conditioned media to Sertoli cells, small (2- to 2.6-fold, respectively) but significant (p < 0.02) increases in extracellular cAMP levels were observed. Although both FSH and forskolin activated c-fos and PPenk gene expression in Sertoli cells, the germ cell factor(s) that stimulated PPenk mRNA levels did not affect the expression of this oncogene. These results indicate that germ cells interact with Sertoli cells, possibly by a protein(s) that acts as a short-loop paracrine factor, which regulates the expression of PPenk gene in Sertoli cells. These data suggest that stage-specific regulation of PPenk levels in Sertoli cells may occur in vivo.