Influence of Estrogen on Anterior Pituitary Lactogen Production in vitro ∗

Summary

Addition of estradiol 17-B to the medium of anterior pituitaries cultured in vitro for 3 days resulted in a decrease in lactogen production. Estradiol levels of 0.1, 0.5, and 5.0 μg/ml of medium lowered lactogen production 16.7, 23.9, and 27.3%, respectively, below that noted for controls. The administration of 1 and 10 μg of estradiol/ day for 10 days in vivo, and subsequent cul-turing of pituitaries from these animals in vitro, resulted in a lactogen production 31.6 and 27.6% higher, respectively, than that of the control. Co-cultures of anterior pituitaries and hypothalami with estradiol in the medium (0.5 μg/ml) did not significantly alter lactogen production from that noted for the control. Electrophoretic separation of the proteins present in lyophilized control medium revealed the presence of 4 components, the most prominent of which was the second. In cultures where estradiol was added to the medium, electrophoretic separation indicated that the second component was now equal in intensity to that of the third. Lyophilized medium from cultures in which pituitaries were estrogenized in vivo resulted, when separated electrophoretically, in the second component being more intense than the second component of control medium. The intensity of the second protein component appeared to be related to the lactogen content of the medium. It is believed that lactogen stimulating effect of estrogen in vivo is not directly on the anterior pituitary but acts indirectly, probably through the hypothalamus.