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Biology of Reproduction, Vol 14, 212-218, Copyright © 1976 by Society for the Study of Reproduction

Control of the LH Receptor by Prolactin and Prostaglandin F2agr in Rat Corpora Lutea

DANIEL L. GRINWICH 1, MARTIN HICHENS 1, , and HAROLD R. BEHRMAN 1

1 Department of Reproductive Biology, Merck Institute for Therapeutic Research, Rahway, New Jersey 07065


Functional corpora lutea were induced in 28 day old, female rats with 4 iu of pregnant mare's serum, followed 72 h later with cervical stimulation. PGF2agr (3 mg/kg) and ergocryptine (2 mg/kg) were administered (sc) 7 days following cervical stimulation. Prolactin (NIH-S11; 2 iu) was administered on the same day 4 h before, and 3 and 15 h after drug treatment. Animals were sacrificed at either 2, 8 or 24 h following treatment with PGF2agr or ergocryptine. Serum progesterone was significantly depressed (P<0.05) at 2, 8 and 24 h (12.1 ± 0.6, 14.9 ± 1.4 and 10.5 ± 0.5 ng/ml, respectively) after PGF2agr treatment from the 0 h concentration of 40.5 ± 12.4 ng/ml. Serum 20agr-ol was unchanged at 2 h (11.2 ± 5.6 ng/ml), but was significantly elevated (P<0.01) at 8 (37.8 ± 4.7 ng/ml; P<0.01) and 24 h (52.6 ± 8.5) after PGF2agr treatment. The LH receptor was decreased 16, 30 and 72 percent at each respective time period but the change was not significant 2 h after PGF2agr treatment. Simultaneous treatment of the animals with prolactin blocked the effect of PGF2agr on serum progesterone and the LH receptor when animals were sacrificed 24 h after PGF2agr treatment.

Ergocryptine caused a significant drop (P<0.05) in serum progesterone 2 h after treatment (30.4 ± 6.2 ng/ml) which became more pronounced at 8 (12.7 ± 6.3 ng/ml) and 24 h (10.4 ± 3.5 ng/ml) from the 0 h control level of 68.5 ± 17.4 ng/ml. Ergocryptine had no effect on gonadotropin binding capacity at 2 or 8 h, but 24 h after treatment the corpus luteum LU receptor was decreased 70 percent (P<0.005). Simultaneous treatment of animals with prolactin produced a complete block of the ergocryptine effect on serum progesterone and the corpus luteum LH receptor. These data were interpreted as evidence for a direct role of prolactin in regulation of the corpus luteum LH receptor in the rat and may be the mechanism of the cooperativity known to exist between these gonadotropins. The early depression of serum progesterone by PGF2agr appears not to be due to a loss of LH receptor. Loss of the LH receptor was directly correlated with the first appearance of functional luteolysis (elevated 20agr-ol) which indicates this is a possible mechanism to ensure that luteolysis continues once initiated and would explain the continued progression of luteolysis hours after PGF2agr treatment.

Note:
ACKNOWLEDGMENT The authors thank the NIAMDD for supply of prolactin.

Submitted on June 10, 1975
Accepted on October 10, 1975






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Copyright © 1976 by the Society for the Study of Reproduction.