The influence of progesterone on the antidiuretic and oxytocic activities of the posterior pituitary lobe of female rats.

Mature, female rats received 2 mg progesterone i.m. during proestrus and estrus and 4 mg during all stages of the sexual cycle. 24 h after injection the animals were decapitated. Antidiuretic and oxytocic activities of the posterior pituitary lobe were tested by bioassay. The increased hormone content of the neurohypophysis in reaction to progesterone administration is explained by an inhibiting effect of progesterone on hormone secretion. The physiological and possible pathophysiological importance of this effect is discussed, expecially with regard to the genesis of cyclic edema and late pregnancy gestosis.