Distribution of the oestrogen induced protein and of total protein between endometrial and myometrial fractions of the immature and mature rat uterus

Using two methods for preparation of endometrial and myometrial tissue fractions, a new method based on mincing and gentle maceration of the immature rat uterus, or separation by dissection of endometrium and myometrium from the mature uterus, both controlled histologically, The authors analysed the distribution of the estrogen induced protein (IP), and total protein and DNA in these endometrial and myometrial fractions. Studies with both immature and mature estrogen stimulated uteri indicate that IP is synthesized in both the endometrial and myometrial tissues. In the immature uterus, there was a marked enrichment of IP in the endometrial fraction. When macerated for 20 or 50 sec, 60-70% of the total IP, 5% of the total DNA, 9% of the total protein, and 24-30% of the total soluble protein were found in the endometrium. This enrichment is shown to be due most likely to preferential synthesis of IP in the endometrium. In contrast, in the mature uterus, there was no significant enrichment of IP in the endometrium. Since IP synthesis is associated with the action of estrogen on both endometrium and myometrium, and the ultimate physiological effects of estrogen on the two tissues seem to be different, the divergence of the action of estrogen in these tissues may occur at some point after IP synthesis.