ADRENERGIC REGULATION OF ESTRADIOL UPTAKE AND CYCLIC GMP CONTENT IN RAT UTERUS

The presence of adrenergic regulation of estradiol uptake in rat uterus was studied by using α- and β-adrenergic blockers in normal or Ca2+-free Tyrode’s solution at 30°C in vitro. Cyclic GMP content was also investigated under these conditions. By the stimulation with noradrenaline (4×10−7 M), Ca2+-dependent 3H-estradiol uptake was increased in both cytosol and nuclear fractions. These increases were blocked inthe presence of phentolamine (4×10−7 M) but not by propranolol (4×10−7 M). Increase in uterine cyclic GMP contents were shown under the condition in which 3H-estradiol uptake was stimulated. These results suggest that adrenergic α-stimulation increased uterine estradiol uptake and that consequently, increased estradiol-receptor complexes elevated uterine cyclic GMP levels. The changes in uterine cyclic GMP may serve as an index of estrogen action.