抄録
As a general secretion pattern of gestagen during the functional luteal phase inthe rat, the level of progesterone is always high and that of 20α-hydroxypregn-4-en-3-one (20α-OHP) is low. Thus, the reciprocal relationship is generally observed between two steroids. In the midpregnancy corresponding to the time of placentation, however, the characteristic pattern of gestagen secretion was observed as an exception, i. e. in parallel with progesterone, the level of 20α-OHP also rises.
Hypophysectomy performed at 12 day of pregnancy, did not alter this characteristic secretory pattern. The luteotrophic factor which resulted in parallel rise of progesterone and 20α-OHP at this stage, therefore, was not seem to be the pituitary origin. Hysterectomy in addition to hypophysectomy, caused significant decrease of both steroids and nullified the parallel rise. The luteotrophic factor seemed to be secreted from pregnant uteri. Pregnant uteri from which fetuses alone were removed, however, could not produce the parallel rising of two steroids, though the secretion was continued in some extent and showed almost the same level with that of pseudopregnant rats bearing deciduomata.
The fetuses are considered to be essential to form the endocrine milieu which bring about the characteristic pattern of gestagen secretion at midpregnancy, and this luteotrophic factor might be produced and secreted as the results of an interaction between placentae and fetuses.
