Expression of messenger ribonucleic acids that encode for 3 beta-hydroxysteroid dehydrogenase and cholesterol side-chain cleavage enzyme throughout the luteal phase of the macaque menstrual cycle.

To study further the control of the primate corpus luteum, we obtained corpora lutea from cynomolgus macaques at defined stages of the luteal phase and examined steady state mRNA levels in these corpora lutea by Northern analysis for the two major enzymes involved in progesterone biosynthesis, cytochrome P450 cholesterol side-chain cleavage (P450SCC) and 3 beta-hydroxysteroid dehydrogenase (3 beta HSD). mRNAs for both P450SCC and 3 beta HSD were maximal or near maximal shortly after ovulation and luteinization (days 3-5 of the luteal phase). mRNA for P450SCC exhibited a slight, but nonsignificant (P greater than 0.05) decline throughout the remainder of the luteal phase and was undetectable upon luteal regression. Steady state levels of 3 beta HSD mRNA were significantly lower (P less than 0.05) from corpora lutea removed during the midluteal phase (days 7-8 of the luteal phase) than those in newly formed corpora lutea and declined to 10% of early luteal phase values by days 13-15 of the luteal phase. 3 beta HSD mRNA levels fell to nondetectable values upon luteal regression. These results reveal a paradoxical relationship between the steroidogenic activity of the primate corpus luteum in vivo and the steady state levels of the mRNAs that encode for the major enzymes involved in progesterone biosynthesis. Unlike serum progesterone concentrations, which are very low immediately after ovulation and then rise during the midluteal phase, the steady stale levels of P450SCC mRNA and 3 beta HSD appeared to be maximal or near maximal shortly after ovulation and declined throughout the remainder of the luteal phase. These findings are consistent with the notion that luteal lifespan is set at the time of ovulation and luteinization, and the decline in luteal function may be due in part to decay of specialized luteal cell mRNAs with finite half-lives.

Acute suppression of FSH secretion by oestradiol in the ovariectomized rhesus monkey.

Using long-term ovariectomized rhesus monkeys, we examined the ability of oestradiol to decrease circulating FSH concentrations in the absence of other ovarian factors. Daily blood samples were obtained from untreated monkeys for 8 days, followed by insertion of oestradiol capsules after the Day-8 sample was taken. Samples were then taken on Days 9-15, the capsules were removed after the Day-15 sample, and samples were obtained on Days 16-19. Serum was assayed for concentration of oestradiol, FSH and LH by RIA. The concentration of FSH (ng/ml) in serum did not change during the first 8 days before oestradiol treatment (overall mean = 356 +/- 55) but decreased from the Day-8 value of 320 +/- 8 to 190 +/- 42 on Day 9 and by Day 15, after 7 days of oestradiol treatment, had reached a nadir of 20 +/- 5. By Day 17, i.e. 2 days after removal of the oestradiol capsules, serum FSH had increased (P less than 0.05) to 92 +/- 23 with a further increase (P less than 0.05) on Day 19 (171 +/- 16). This study demonstrates that, unlike in rats, mice, and sheep, administration of oestradiol alone to ovariectomized rhesus monkeys reduces immunoreactive serum FSH to concentrations measured in intact animals.

Localization of inhibin/activin subunit mRNAs within the primate ovary.

In order to gain further understanding of the physiology of inhibin and activin in the primate, the expression of inhibin/activin subunit mRNAs in the monkey ovary was examined by in situ hybridization. Granulosa cells of small antral follicles were found to express mRNA for the beta B subunit, which decreased to undetectable levels in dominant follicles. In contrast, expression of alpha and beta A subunit mRNAs was detected in granulosa cells of dominant follicles and in corpora lutea, but not in small antral follicles. These results indicate that the expression of the beta A and beta B subunits is differentially regulated during the growth and development of ovarian follicles in the monkey.

Developmental expression of Ca++/Mg++-dependent endonuclease activity in rat granulosa and luteal cells.

A Ca++/Mg++-sensitive endonuclease has been associated with programmed cell death in a variety of endocrine and non-endocrine dependent tissues. In view of the remarkable similarity of the process of the regression of the corpus luteum and other models of programmed cell death, we studied the occurrance of this endonuclease activity in granulosa cells at different developmental states and the corpus luteum. Our results show that while undifferentiated granulosa cells do not express this endonuclease activity, treatment with pregnant mares serum gonadotropin results in a rapid increase in endonuclease activity that is maintained following ovulation and luteinization of granulosa cells.

Metabolism of testosterone in vivo in the pregnant rat.

The metabolism of testosterone (T) was examined during the second half of pregnancy in the rat to determine whether utilization of T for estradiol (E2) synthesis occurs via conversion of T to androstenedione (A). On Days 11, 16, and 21 of gestation (term = Day 23), rats (n = 7-9/group) were anesthetized and a constant infusion of [3H]T was initiated. At 60 min, blood was obtained from a jugular vein and the ovaries (Days 11, 16, and 21), and placentae and uterine tissue (Day 16 only) were removed. In a second study performed in rats on Day 16 of gestation (n = 8-10/group), the ovaries and/or gravid uterus were removed 15 min after initiation of [3H]T infusion, and blood was taken from a jugular vein 60 min later. Radiolabeled T and A were purified from serum and tissues by paper chromatography. In a third group of rats (n = 6), jugular vein samples were obtained sequentially on Days 11, 16 and 21 of gestation and serum concentrations of T were measured by radioimmunoassay. The metabolic clearance rate of T was constant during the study period (overall mean = 31 1/day). In contrast, the serum concentration of T (pg/ml) on Day 16 of gestation (863 +/- 108) exceeded (p less than 0.02) that on Day 11 (445 +/- 74); the latter was similar to that measured on Day 21 (592 +/- 109). Thus, the estimated production rate of T was greatest on Day 16 of gestation.(ABSTRACT TRUNCATED AT 250 WORDS)

Uterine metabolism of estradiol in vivo during early pseudopregnancy in the rat.

We measured the concentration of [3H]estradiol (E2) and its conversion to [3H]estrone (E1) in endometrium and myometrium at diestrus, estrus, and Days 2-6 of pseudopregnancy (PSP) in the rat. Animals (N = 5-10/group) were anesthetized with pentobarbital and a constant infusion of [3H]E2 initiated via a jugular vein. Following attainment of isotopic equilibrium, a blood sample was obtained from the inferior vena cava, the endometrium and myometrium isolated, and [3H]E2 and [3H]E1 content determined after purification by paper chromatography. The metabolic clearance rate of E2 and the peripheral conversion of E2 to E1 (% Cr E2----E1), remained relatively constant throughout the study period. Regardless of the reproductive status of the rat, endometrial and myometrial [3H]E2 and [3H]E1 concentrations (cpm/g) were greater (P less than 0.001) than respective values (cpm/ml) in serum. At estrus, the concentration of [3H]E2 in the endometrium was lower (P less than 0.05) than that at diestrus. In contrast, endometrial % Cr E2----E1 and weight of the endometrium were both greater (P less than 0.05) at estrus than at diestrus. Similar patterns were measured in the myometrium. During PSP, the concentration of [3H]E2 in the endometrium increased (P less than 0.05) from Day 2 to Day 6 whereas concentrations in the myometrium remained relatively constant. Endometrial weight increased (P less than 0.05) between Days 2-4 of PSP and was associated with a concomitant decrease (P less than 0.05) in the % Cr E2----E1 from 59 to 22%. The % Cr E2----E1 in the myometrium (2-4%) was constant between Days 2-4 of PSP but increased to 10% by Day 6 in association with a decrease (P less than 0.05) in weight of the myometrium. We have demonstrated in vivo that growth and differentiation of the uterine endometrium during early pseudopregnancy in preparation for implantation/deciduogenesis is associated with decreased endometrial % Cr E2----E1. Because ovarian E2 production is markedly decreased during early PSP, we suggest that a decrease in uterine metabolism of E2 may act, in part, to maintain endometrial E2 at concentrations sufficient to permit receptor interaction.

Utilization of circulating androstenedione and testosterone for estradiol production during gestation in the rat.

The placenta provides androgen precursors for ovarian estradiol (E2) production during the second half of gestation in the rat. However, no studies have measured E2 synthesis in vivo from circulating testosterone (T) or androstenedione (A) before or after Day 12 of gestation. In addition, it is not known whether the placenta near term continues to serve as the major source of androgens. Therefore, we measured the ovarian conversion of circulating T and A to E2 in vivo on Days 11, 16, and 21 of gestation (term = Day 23). Rats (N = 6-8/group) were anesthetized with pentobarbital and a constant infusion of [3H]T or [3H]A initiated via a jugular vein. After isotopic equilibrium was achieved at 60 min, blood samples were obtained from the contralateral jugular (J) vein and a uterine-ovarian (UO) vein, and the ovaries were removed. In a second group of rats on Day 16 of gestation, either the gravid uterus or both ovaries were removed after initiation of isotope infusion, and blood samples obtained 60 min later. Radiolabeled T, A, and E2 were isolated and purified by sequential paper chromatography. The concentration of [3H]E2 following infusion of either androgen was greater in the UO vein than in the J vein on Days 16 and 21 (p less than 0.02), but not on Day 11, of gestation. In animals infused with [3H]T, [3H]E2 (cpm/ml) in UO vein increased (p less than 0.001) from 84 +/- 33 (mean +/- SE) on Day 11 to 357 +/- 30 and 312 +/- 46 on Days 16 and 21, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)