Abstract
Previous experiments 1 , 2 , 3 , 4 have shown that the mucification of the vagina which is usually observed in pregnant rats may be elicited during lactation if large doses of oestrin are administered. Since administration of similar doses of oestrin in ovariectomized rats would lead to cornification of the vaginal epithelium, the mucification reaction was ascribed to the simultaneous action of oestrin and corpus luteum hormone. Similarly the epithelial lining of the uterus shows only a moderate degree of progestational proliferation during lactation or pseudo-pregnancy in the rat, while in the second half of pregnancy the proliferation of the endometrium and the growth of the uterus in toto is much more marked and of a different nature. Various reasons which are discussed in more detail in the papers quoted above led us to the conclusion that the endometrial changes during lactation, pseudo-pregnancy, and early pregnancy, are mainly due to the hormone of the corpus luteum, and we called this reaction “the first stage of progestational proliferation.” The “second stage of progestational proliferation” is that observed during late pregnancy, which we believed to be caused by the simultaneous action of corpus luteum hormone and oestrin. We concluded from indirect evidence that oestrin is produced in large quantities during late pregnancy in the rat but not during lactation or early pregnancy. This would explain why vaginal mucification and the second stage of progestational proliferation appears in late pregnancy only and not during early pregnancy or lactation.
Get full access to this article
View all access options for this article.