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Luteinizing Hormone Receptor Number and Affinity in Corpora Lutea from Prepuberal Gilts Induced to Ovulate and Spontaneous Corpora Lutea of Mature Gilts¹

University of Georgia, Athens 30602 and U.S. Department of Agriculture, Athens, GA 30613

Abstract

This study was designed to determine if luteal cell receptors for luteinizing hormone/human chorionic gonadotropin (LH/hCG) contribute to the previously demonstrated abnormal function of induced corpora lutea (CL) in gilts. Twenty-five prepuberal (P) gilts, induced to ovulate with 1,500 IU pregnant mare serum gonadotropin followed 72 h later with 500 IU hCG (d 0 = day of hCG), and 22 mature (M) gilts that had displayed two or more estrous cycles were ovariectomized (OVX) on d 10, 14, 18, 22 or 26 after the onset of estrus. All gilts except those OVX on d 10 were hysterectomized between d 6 and 9 to ensure luteal maintenance. The CL were stored at –196° C until determination of LH/hCG receptor number and dissociation constant (K_D) by saturation analysis. Receptor number was greater for M than for P gilts on d 14 (P < .07) and d 18 (P < .01). The K_D was greater in M than in P gilts on d 14 (P < .01) and d 18 (P < .0001). The LH/hCG receptor number and K_D of P gilts remained the same throughout the days studied. The LH/hCG receptor number (fmol/mg protein) of M gilts was elevated on d 10, 14, and 18 (50.8, 50.4 and 51.4, respectively) and decreased on d 22 (26.5) and d 26 (25.4) to values similar to those of P gilts. In M gilts, K_D increased on d 14, remained high on d 18 and decreased on d 22. We suggest that abnormal function of induced CL in P gilts may be due to an elevated LH receptor number.

¹ This research was supported by State and Hatch funds allocated to the Georgia Agric. Exp. Sta. and by USDA funds.

² Dept. of Anim. and Dairy Sci.

³ To whom reprint requests should be addressed, Anim. and Dairy Sci. Dept., Livestock-Poultry Bldg., Univ. of Georgia, Athens 30602.

⁴ Richard B. Russell Agric. Res. Center, USDA-ARS.