Postovulatory steroidogenesis after ovulation induced by LH or FSH in hypophysectomized pro-oestrous hamsters

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Abstract
Hamsters hypophysectomized (hypox.) and concurrently injected i.p. with 2.5 .mu.g ovine luteinizing hormone [LH] or 25 .mu.g ovine follicle stimulating hormone [FSH] at 1300 h on the day of pro-estrus ovulated the normal complement of ova the next morning (day 1). At 0900 h on day 1, serum progesterone levels were comparable between sham-hypox. and LH-treated hypox. hamsters. There were no differences in serum progesterone between FSH-treated or saline-treated hypox. hamsters; a slight but significant increase in serum progesterone occurred at 1500 h in the FSH-treated animals and this was continued on day 2, when values were comparable to those in the LH-treated and sham-hypox. hamsters. The corpus luteum [CL] induced by LH or FSH produced significant amounts of progesterone in vitro on day 1 at 0900 and 1500 h. On day 2, there was a significant increase in progesterone production by the CL of both groups. Production rates of progesterone on CL in vitro were the same in the LH- and FSH-treated animals on days 1 and 2. Once ovulation occurred in the hamster the newly developed CL gained the ability to synthesize, store and secrete progesterone independently of pituitary hormones for 2 days, although at a delayed rate after FSH treatment. The results of incubations of the non-luteal (residual) ovarian tissues showed that large quantities of progesterone (about 7 ng/mg per h) were produced by day 1 by tissue from FSH-treated animals while that of LH-treated hamsters lost progesterone at the rate of about 1 ng/mg per h. In saline-treated hypox. hamsters the residual tissue produced large amounts of progesterone and small amounts of estradiol-17.beta. and testosterone in vitro for at least 2 days after hypox. Little estradiol-17.beta. was produced by the CL of hamsters treated with LH, FSH or sham-hypox. By day 2 the CL of all 3 groups produced appreciable amounts of testosterone in vitro, whereas on day 1 only the CL induced by LH secreted testosterone.