In order to ascertain which ovarian cell type within the follicle is the source of preovulatory estrogen secretion in vivo, ovarian venous, as well as peripheral venous, blood was collected prior to, 5 min, 30 min, and 120 min after the removal of follicular fluid and granulosa cells from 17 monkeys. In addition, estrogen, progesterone, and progestins were measured in the peripheral blood, ovarian venous blood, and follicular fluid of the follicle-containing and contralateral ovary in 24 monkeys, in order to prove that the preovulatory follicle is the principal source of estrogen. Estradiol was the principal estrogen and was secreted in larger amounts by the ovary with the large preovulatory follicle (7-10 mm in diameter) compared with the contralateral ovary. In 15 experiments ovarian venous estrogen (3934 +/- 798 pg/ml, mean +/- SE) in the vein draining the large follicle-containing ovary was usually 5-15-fold higher than peripheral plasma estrogen levels which were 307 +/- 31 pg/ml. The contralateral ovary secreted a small amount of estrogen (654 +/- 162 pg/ml). Follicular fluid contained large amounts of estrogen (2754 +/- 695 ng/ml) with levels which did not always correlate well with peripheral plasma or ovarian venous estrogen. Ovaries containing non-preovulatory or recently ovulated follicles secreted less estrogen. The removal of granulosa cells and follicular fluid from the preovulatory follicle led to no significant decrease (P greater than 0.5) in ovarian venous secretion of estrogen after a 5, 30, or 120 min time interval. This would indicate that, within the time constraints of this experiments, the follicular fluid and granulosa cells contribute relatively little to ovarian venous estrogen and that thecal cells of the large preovulatory follicle alone can secrete more of the estrogen into the ovarian vein.
The steroidogenic effects of bovine luteinizing hormone (lh) and human chorionic gonadotrophin (hcg) in vivo were investigated by measuring the concentration of progesterone in peripheral plasma as an index of luteal secretory activity. The gonadotrophins were injected intravenously on Days 5, 10, 15 and 20 of the oestrous cycle, and serial samples of peripheral blood obtained before and after the injections. The steroidogenic response to lh or hcg was variable. Statistically significant increases in plasma progesterone levels were produced in five out of ten experiments; the magnitude of this increase was less than 100% in three cases and the duration of stimulation was less than 3 hr in four cases. The lifespan of the corpus luteum was prolonged and new ovulations were induced by the gonadotrophins.
A tracer dose of the presumptive uterine luteolytic factor (PGF2\g=a\) was introduced into the anterior uterine vein of twelve ewes, either as a bolus or as a 40to 60-min infusion (0\m=.\2\g=m\Ci/min). The ipsilateral ovary was left attached to or disconnected from its ligaments. Neither a bolus nor an infusion of [9-3H]PGF2\g=a\ led to any transfer of radioactivity in the ovarian artery under controlled experimental conditions. These results show conclusively that diffusion, filtration, counter-current exchanges and active transport do not occur between the anterior uterine vein, the utero-ovarian vein and the ovarian artery. A direct and local luteolytic action of PGF2\g=a\ is therefore questionable.
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