ESTROGEN ACTION VIA THE CAMP SIGNALING PATHWAY - STIMULATION OF ADENYLATE-CYCLASE AND CAMP-REGULATED GENE-TRANSCRIPTION

Estrogenic hormones, believed to exert most of their effects via the d irect interaction of their receptors with chromatin, are found to incr ease cAMP in target breast cancer and uterine cells in culture and in the intact uterus in vivo. Increases in intracellular cAMP are evoked by very low concentrations of estradiol (half maximal at 10 pM) and by other physiologically active estrogens and antiestrogens, but not by an inactive estrogen stereoisomer. These increases in cAMP result from enhanced membrane adenylate cyclase activity by a mechanism that does not involve genomic actions of the hormones (are not blocked by inhib itors of RNA and protein synthesis). The estrogen-stimulated levels of cAMP are sufficient to activate transcription from cAMP response elem ent-containing genes and reporter plasmid constructs. Our findings doc ument a nongenomic action of estrogenic hormones that involves the act ivation of an important second-messenger signaling system and suggest that estrogen regulation of cAMP may provide an additional mechanism b y which this steroid hormone can alter the expression of genes.