Adenovirus-directed expression of functional luteinizing hormone (LH) receptors in undifferentiated rat granulosa cells: Evidence for differential signaling through follicle-stimulating hormone and LH receptors

This study was conducted to determine the feasibility of using replication- defective adenovirus vectors to express receptors for LH. Two vectors were constructed, one that directs the expression of wild-type human LH receptor (LHr; AdRSVLHrwt) and another that directs the expression of the constitut ively activated D578H mutant human LH receptor (AdRSVD578HLHr). When infect ed with AdRSVwtLHr and AdRSVD578HLHr, COS-1 cells expressed LW hCG-binding sites as reflected by specific binding of [I-125]hCG. TO determine the abil ity of the vectors to confer LH responsiveness, undifferentiated rat granul osa cells, which possess only FSH receptors, were infected with AdRSVwtLHr and AdRSVD578HLHr. Expression of the constitutively activated D578H LHr inc reased basal (gonadotropin-independent) estrogen and progesterone productio n. Expression of the wild-type LHr in granulosa cells did not stimulate bas al steroid production, but conferred responsiveness to exogenous LH. For bo th wild-type LHr and D578HLHr, the absolute levels of steroid production we re dependent upon the input of viral titers. Using these vectors, we compared effects of FSH and LH receptor activation in undifferentiated granulosa cells. Stimulation of undifferentiated granul osa cells by FSH and D578HLHr, as well as activation of wild-type LHr with LII resulted in comparable production of progesterone. In contrast, estradi ol production in cells stimulated with FSH was greater than that in cells t hat expressed either D578H receptors or wild-type LHr in the presence of LH . Analysis of messenger RNAs (mRNAs) revealed that activations of FSH and t he LH receptors were comparable in the induction of alpha -inhibin and 3 be ta -hydroxysteroid dehydrogenase mRNAs. However, activation of FSH receptor led to significantly greater expression of P450 aromatase and LHr mRNAs th an did activation of LHr. These results suggest that activation of FSH and LH receptors in granulosa cells may differ with respect to activating intra cellular signaling pathways and stimulating gene expression.