ROLE OF ESTROGEN RECEPTOR-ALPHA IN THE ANTERIOR-PITUITARY GLAND

Targeted insertional disruption of the mouse estrogen receptor-alpha ( ER alpha) gene has provided a genetic model in which to test hypothese s that estrogens exert important effects in development and homeostati c functions of the anterior pituitary gland, particularly in the lacto troph and gonadotroph cell types. Analysis of ER alpha gene-disrupted mice reveals a marked reduction in PRL mRNA and a decrease in lactotro ph cell number, but normal specification of lactotroph cell phenotype. Gonadotropin mRNA levels in ERR alpha gene-disrupted female mice are elevated, consistent with previously described transcriptional suppres sion of gonadotropin subunit gene expression in response to sustained administration of estrogen in wild type mice. These results provide ge netic evidence that ER alpha plays a critical role in PRL and gonadotr opin gene transcription and is involved in lactotroph cell growth, but is not required for specification of lactotroph cell phenotype.