CHANGE FROM BETA-ADRENERGIC TO ALPHA-ADRENERGIC GLYCOGENOLYSIS INDUCED BY CORTICOSTEROIDS IN FEMALE RAT-LIVER

The conversion of beta- to alpha-adrenergic glycogenolysis by corticos teroids was studied in perfused livers of mature female rats. Isoprote renol stimulated glucose production more effectively in female rats th an in male rats, but the difference in its stimulatory effect disappea red in adrenalectomized (ADX) rats, whereas it remained in adrenodemed ullated rats. When ADX female rats were treated with dexamethasone sul fate, alpha-responses increased and beta-responses decreased, dependin g on the concentration of dexamethasone sulfate. The treatment of fema le rats with 1.5 mg/kg dexamethasone sulfate changed the levels of the alpha- and beta-responses to those observed in male rats, and the cha nges were associated with changes in the number of receptors. Although periodicity of changes in plasma corticosterone levels was observed i n both male and female rats, the extent of circadian variations was si gnificantly lower in female rats during the estrous cycle than in male rats. The variations in plasma corticosterone levels and in both alph a- and beta-responses after ovariectomy approached those in male rats. The results suggest that the level of plasma corticosterone might pla y an important role in the regulation of the relative levels of alpha- and beta-adrenergic responses in female rats.