Effect of progesterone on adrenoceptors in the isthmus of the rabbit oviduct.

The effect of adrenergic agonists on the contractility of circular muscle of the isthmus of the oviduct was studied in isolated tissues from rabbits in estrus and after progesterone pretreatment. alpha-Adrenoceptor sensitivity was not altered by progesterone, and the order of potencies of alpha-agonists was similar to that for alpha-adrenoceptors in other rabbit tissues. Progesterone pretreatment increased the maximal inhibitory effect of isoprenaline on beta-adrenoceptors, but did not alter sensitivity to the agonist, suggesting that there had been an increase in the number of beta-adrenoceptors rather than a change in their affinity. The order of potencies of beta-agonists was similar to that for the beta1-adrenoceptor in other rabbit tissues.