STUDIES CONCERNING THE MECHANISM CONTROLLING THE INITIATION OF LACTATION AT PARTURITION I. CAN ESTROGEN SUPPRESS THE LACTOGENIC HORMONE OF THE PITUITARY?1,2

Publisher Website
Google Scholar
Abstract
I. The adm. of large dosages of diethylstilbestrol (2 mg. daily) and testosterone propio-nate (2 mg. daily) to lactating rats for the 1st 6 days post partum increased the content of lactogenic hormone in the pituitary, caused some reduction in the amt. of milk present in the mammary glands, and resulted in the death of 38 and 11% respectively of the young rats. Injection of total amts. of diethylstilbestrol ranging from 0.0125 to 100.00 mg. into normal immature and mature c? guinea pigs increased the lactogen content of the pituitary. Lower dosages of hormone resulted in greater increases in the lactogenic hormone (up to 438%) than was secured with the higher dosages (22-84% increase). The adm. of low, moderate, or huge amts. of estrogens will not produce a decrease in the secretion of lactogenic hormone by the pituitary. Parturient rats which were not suckled for the 1st wk. after parturition contained 50% less pituitary lactogen than suckled rats, and their mammary glands were practically devoid of milk. This explains why lactation will cease when suckling is discontinued. It also explains why the clinical reports on the suppression of lactation with hormones are difficult to evaluate.[long dash]II. In immature [male] guinea pigs progesterone alone had no effect on the lactogen content of the pituitary; estrone alone elicited definite increases in the lactogen content of the pituitary; suitable combinations of progesterone and estrone either entirely prevented or reduced the increase in lactogenic hormone which could be obtained with estrone alone. These results are believed to explain why the lactogen content of the pituitary remains as low during pregnancy as in the non-pregnant state. The progesterone-estrogen ratio is believed to be such that progesterone overrides the lactogen stimulating effects of estrogen. As a result, the amt. of lactogenic hormone in the pituitary during pregnancy remains insufficient to initiate an abundant lactation.[long dash]III. The effect of length of estrogen treatment on the lactogen content of the pituitary was detd. in 40 [male] guinea pigs, divided into 8 equal groups. All guinea pigs received the same total amt. of estrone (0.3 mg.) over periods of time varying from 1-30 days. A 142 and 204% increase in lactogenic potency of the pituitary was obtained in the groups injected for 1 and 2 days respectively, whereas a 371% increase was secured in the animals injected for 5 days. The animals injected for 10-30 days did not show a significantly greater increase than was observed in the 5 day group. These results indicate that estrogen can account for the rapid increase found in the lactogen content of the pituitary of rats, guinea pigs and rabbits 2-5 days post partum. 4 New Zealand white rabbits were hysterectomized on the 20th day of pregnancy, and were killed 5 days later. Individual assays of the pituitaries revealed that an avg. increase of 83% of lactogenic hormone had been obtained, indicating that the predominant influence of progesterone during pregnancy must be removed before estrogen can effect an increase in the lactogen content of the pituitary.

This publication has 1 reference indexed in Scilit: