Up-regulation of guinea pig myometrial adenylate cyclase activity by intrauterine estradiol and progesterone pellets.

The effects of intrauterine implantation of 17 beta-estradiol and progesterone on basal and stimulated adenylate cyclase activity in guinea pig myometria were studied in nonpregnant, previously oophorectomized guinea pigs receiving intrauterine implants of either estradiol, progesterone, a combination of the two hormones, or placebo for 7 days. Guanine nucleotides resulted in a significant increase in basal enzymatic activity. The extent of enzymatic stimulation in estradiol-treated animals was significantly higher than that observed in either controls, animals receiving progesterone, or a combination of estradiol and progesterone. Sodium fluoride stimulation occurred in all treatment groups to a similar degree. However, guanine nucleotides resulted in a significant decrease in percent stimulation of maximal sodium fluoride-stimulated enzymatic activity. Finally, beta-adrenergic receptor-mediated enzymatic activity, as assayed by isoproterenol stimulation, was higher in those animals that received estradiol implants than in controls or the other two hormonally treated groups. Intrauterine administration of these sex steroid hormones, directly or indirectly, modulates myometrial adenylate cyclase activity.