D. J. Dierschke

Sexual Differentiation of Pituitary Function: Apparent Difference between Primates and Rodents

Surges in luteinizing hormone secretion resembling those which occur spontaneously during the menstrual cycle were induced by acute elevations in circulating estrogen concentrations in both male and female rhesus monkeys gonadectomized in adulthood. These experiments demonstrate that in primates, in contrast to rodents, exposure of the hypothalamohypophyseal unit to androgens throughout fetal and postnatal development does not prevent the differentiation of the control system that governs cyclic gonadotropin secretion.

Periparturitional serum concentrations of prolactin, the gonadotropins, and the gonadal hormones in the rhesus monkey.

Summary The time courses of serum concentrations of prolactin, estradiol, estrone, progesterone, LH, and FSH were studied in seven pregnant rhesus monkeys from 1 month prior to delivery until 1 month after parturition. All animals nursed their young. Circulating levels of estradiol and estrone increased during the last few days of pregnancy, reaching peak values of 700 pg/ml and 350 pg/ml, respectively, on the day prior to delivery, fell precipitously to about 25 pg/ml within 1 day after parturition, and remained at this level for at least 30 days. Serum prolactin concentrations also increased during the week preceding parturition, rose abruptly at delivery, and then declined gradually. Serum progesterone levels ranged between 2 and 3 ng/ml during the last month of pregnancy, rose slightly a few days prior to parturition, decreased sharply at delivery to 50% of pre-partum levels and declined gradually thereafter. Serum LH and FSH levels were not detectable during the entire sampling period. The administration of estradiol benzoate to two pregnant monkeys at midgestation, in a manner which replicated the normal prepartum increase in serum estradiol concentrations, failed to elicit an elevation in circulating prolactin levels or to induce premature delivery of the fetus. We are indebted to E. Burkett, B. Leeson, C. Tsai, L. Morrison, and to our animal care staff for their expert technical assistance.

Influence of suckling on gonadotropin secretion in the postpartum rhesus monkey.

Summary The increase in serum gonadotropin concentrations which follows ovariectomy in the rhesus monkey is markedly retarded in lactating animals suckling their infants. This inhibitory influence of lactation is more pronounced for LH than FSH. The LH content of the pituitary glands removed from monkeys is 8% of that found in pregestational adult females while the FSH content is not markedly reduced. The expert technical assistance of B. Petro, B. Lee-son, E. Burkett, and L. Morrison and of our animal care staff is gratefully acknowledged.

Endometrial Secretion of Prostaglandins During the Ovarian Cycle and Early Pregnancy

That the prostaglandins are released in human menstrual fluid was first established in a series of studies by Pickles and coworkers during 1959 through 1967 (see Pickles, 1967 for references). Since that time, endometrial or uterine production of prostaglandine has been reported in a variety of mammals, including the ewe, cow, guinea pig, goat (see reviews by Flint and Hillier, 1975 and Horton and Poyser 1976), rat (Weems et al., 1975), mouse (Rankin et al., 1979), mare (Douglas and Ginther, 1976; Vernon et al., 1979a), monkey (Demers et al., 1974), hamster (Saksena et al., 1974) and rabbit (Scommegna et al., 1977; Harper et al., 1978) and in all segments of the oviduct in the hen (Hertelendy and Biellier, 1978). Still, relatively little has been learned about human endometrial secretion of the prosta-glandins and the endocrine control of their secretion is not fully understood in any species.

Metabolic clearance rate of progesterone during lactation in the Rhesus monkey.

Summary No difference in the MCR of progesterone was observed in the follicular and luteal phases of the menstrual cycle in the rhesus monkey. In lactating animals, however, the MCR was increased by 30%. This increase is insufficient to account for the 20-fold difference in circulating progesterone levels in luteal phase and lactating animals.

SEXUAL DIFFERENTIATION OF PITUITARY FUNCTION: APPARENT DIFFERENCE BETWEEN PRIMATES AND RODENTS

Surges in luteinizing hormone secretion resembling those which occur spontaneously during the menstrual cycle were induced by acute elevations in circulating estrogen concentrations in both male and female rhesus monkeys gonadectomized in adulthood. These experiments demonstrate that in primates, in contrast to rodents, exposure of the hypothalamohypophyseal unit to androgens throughout fetal and postnatal development does not prevent the differentiation of the control system that governs cyclic gonadotropin secretion.