On Circulating Sex Steroids During the Estrous Cycle and the Early Pseudopregnancy in the Rat with Special Reference to its Luteal Activation
1974 年 21 巻 1 号 p. 69-79
詳細
1974 年 21 巻 1 号 p. 69-79
Estradiol-17β(E-2), estrone (E-1), progesterone (P), and 20α-hydroxypregn-4-en-3-one (20α-OHP) were measured in peripheral plasma on every 2-4 hr throughout the 4-day estrous cycle and the early pseudopregnancy in rats illuminated 14 hr a day (0500 to 1900). The radioimmunoassay and the competitive protein binding assay were respectively used for the measurements of estrogens and progestins.
In the estrous cycle, E-2 showed a single rise spread from 1600 of diestrus to 1500 of proestrus, where a maximum value at around 0800 of proestrus was followed by an abrupt drop to the basal level by 2000 of the same day. Increasing tendencies of E-1 level at around 2000 of diestrus and around 1800 of proestrus were found, though showing relatively large variations. In progestins in the cycle, P showed significant rises in the evening between 1600 and 2200 every other day, i.e., on the days of proestrus and metestrus. Since daily rises of 20α-OHP were observed between 1600 and 2200 except on the day of proestrus, the total progestin (P 20α-OHP) manifested clear daily rhythmic fluctuation, having a peak every evening in the cycle.
In the first 3 days of pseudopregnancy (PSP), E-2 remained essentially unchanged at a low level, but E-1 showed a significant rise from the late afternoon to the night of Day 1 of PSP. On the other hand, P showed significant rises in the morning (0800) and a much higher rise in the evening (2000) on Day 1 of PSP. The latter rise was also accompanied with the increasing tendency of 20α-OHP. The total progestin did not show appearent daily rhythm during the early PSP. It is revealed that sex steroids patterns during the early PSP are not so simple as hertofore assumed.
Induction of PSP by the single injection of P was possible only at the fixed time (0700-1000) on the day of estrus throughout the estrous cycle. An important role of extraperiodical P secretion found on the day following the cervical stimulation (Day 1 of PSP) was suggested as a possible intervening mechanism for inducing PSP.
