Biology of Reproduction, Vol 21, 1043-1050, Copyright © 1979 by Society for the Study of Reproduction

Changes in Levels of a LH Binding Inhibitor in Aqueous Extracts of Porcine Corpora Lutea as a Function of Aging of the Corpus Luteum

¹ Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201

The 30,000 x g supernatant fraction of aqueous extracts from porcine corpora lutea of old, mid and early luteal phases was investigated to determine its inhibitory activity on the binding of [¹²⁵I]-hCG and on progesterone secretion by granulosa cells harvested from large (6-12 mm) follicles of porcine ovaries. The extracts from old and midcycle corpora lutea had greater ability to inhibit the binding of [¹²⁵I]-hCG than did extracts of early luteal phase corpora lutea. During a 1 h incubation period with tracer hCG, the extracts of late and mid luteal phase corpora lutea exerted a 90% inhibition of [¹²⁵I]-hCG to porcine granulosa cells whereas the extract of early luteal phase corpora lutea exerted a 70% inhibition. Addition of 10% of a 30,000 x g supernatant of old corpora lutea, either directly or after removal of steroids with 0.1% charcoal, inhibited progesterone secretion 90-95% by granulosa cells of large porcine follicles grown for 2 days in monolayer culture. The addition of 1 µg ovine LH along with the extracts from old corpora lutea could not reverse the inhibitory effect. Addition of 10% of a 30,000 x g supernatant of nonluteal ovarian tissue obtained during the mid or late luteal phase inhibited progesterone secretion by cultures of granulosa cells obtained from large follicles after 2-4 days of culture (P<0.01 vs control culture). Addition of LH failed to overcome this inhibitory effect.

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ACKNOWLEDGMENTS This research work was supported by grants from NIH (HD08834) and World Health Organization (Contract No. 77008). G.L.K. was the recipient of an Exchange Worker’s Grant from the World Health Organization. We thank Ms. Sandy Fowler for her very able technical assistance.