Effect of Exogenous Progesterone on the Preovulatory Progesterone Secretion in the Rat

Acute Effects of Various Gonadotropins and Other Pituitary Hormones on Preovulatory Ovarian Progestin Secretion in Hypophysectomized Rats

“…In the rat, a remarkable increase in ovarian progesterone secretion at proestrus was confirmed by other workers (Hashimoto et al, 1968) including ourselves (Uchida et al, 1969). The determination of ovarian progestin secretion and plasma LH level on the same laboratory rats bred under the same condition (Miyake, 1968;Kobayashi et al, 1968;Uchida et al, 1969) has demonstrated that the increase in progesterone secretion at proestrus occurs almost concurrently with an increase in plasma LH level.…”

“…The determination of ovarian progestin secretion and plasma LH level on the same laboratory rats bred under the same condition (Miyake, 1968;Kobayashi et al, 1968;Uchida et al, 1969) has demonstrated that the increase in progesterone secretion at proestrus occurs almost concurrently with an increase in plasma LH level. Furthermore, hypophysectomy at 5.00p.m.…”

A Theoretical Approach to the Regulatory Mechanism in the Brain-Hypophyseal-Gonadal System with Reference to its Mathematical Modeling and Computer Simulation

“…This lower peak is explained as the result of autonomous secretory activities of newly formed corpora lutea (Uchida et al, 1969). In fact, this stage accords with the period, in which the volume of fresh corpora lutea grows to the maximum.…”

“…Now let us consider the regulatory mechanism which governs the PH phase. A steep rise of LH level at proestrus, caused by the sudden increase in LH-RF as described before, then induces not only PH secretion from the ovary, but also suppresses the EH secretion (Uchida et al, 1969). Now the EH phase is replaced by the PH phase.…”

“…Recent studies by Miyake and his associates demonstrated that estrogen (Hori et al, 1968) and progesterone (Uchida et al, 1969) nant stage of estrogen the EH phase and that of progesterone the PH phase ( Figure 5). In the ovary, the follicular growth takes place during the former, while during the latter the follicular maturation, ovulation and luteinization occur successively.…”