The serum levels of progesterone and 20 alpha-dihydroprogesterone, and the ovarian LH, FSH and PRL binding during luteolysis of the superluteinized rat ovary

Torjesen, P.A.; Aakvaag, A.

Acta Endocrinologica 86(1): 162-172


ISSN/ISBN: 0001-5598
PMID: 199009
DOI: 10.1530/acta.0.0860162
Accession: 068523760

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The process of luteolysis was studied in immature rats in which superluteinization had been induced with pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (HCG). Following prostaglandin and prolactin (PRL) in vitro. On day 19 after HCG a marked decrease in the progesterone level from the day 8 level was observed concomitant with a marked increase in 20.alpha.-dihydroprogesterone. The capacity of the ovarian tissue to bind LH in vitro was markedly reduced on day 19 compared to day 8. Identical changes were observed 21 h after 1 mg PG F2.alpha. or PG analogs. Progesterone decreased from about 600 ng/ml to about 50 ng/ml, whereas the increase in 20.alpha.-dihydroprogesterone was from about 200 ng/ml to 500-1000 ng/ml and the reduction in LH binding sites was from 1.7 .times. 10-12-0.5 .times. 10-12 mol/mg protein. Nanogram amounts of the analogs were as effective as 1 mg of PG F2.alpha. The number of FSH or PRL binding sites was not affected by spontaneous luteolysis or the treatment given. By the use of graded doses of the PG analogs a negative correlation (r = -0.81) was found between plasma progesterone and 20.alpha.-dihydroprogesterone levels, and a positive correlation (r = 0.84) between LH binding sites and plasma progesterone levels. The luteolysis induced by PG F2.alpha. or PG analogs was indistinguishable from the spontaneous luteolysis using these parameters.