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Serum Luteinizing Hormone in Prepuberal Gilts After Ovariectomy or Adrenalectomy¹

University of Georgia, Athens 30602 and and US Department of Agriculture, Athens 30613

Abstract

Serum luteinizing hormone (LH) concentrations after ovariectomy (OVX) and adrenalectomy (ADX) were studied in the prepuberal gilt. In Exp. I, gilts, 170 to 175 d of age and 80 to 85 kg body weight, were OVX (n = 5) or sham-OVX (n = 5). Blood samples were collected via jugular vein cannulae every 30 min for 8 h on d 1, 3, 5, 7 and 21 after surgey. In Exp. II, blood samples were collected via jugular vein cannulae every 30 min for 12 h on d 3, 5, 7 and 14 after surgery from five ADX, five sham-ADX and five nonsurgical control gilts of similar ages and weights as in Exp. I. In Exp. I, basal serum LH concentrations ( ± SE, ng/ml) over all days were greater (P<.05) in OVX (2.9 ± .1) than in sham-OVX (1.1 ± .2) gilts. Average basal serum LH concentrations were greater (P<.05) on d 1 for both treatments than all other days sampled. The frequency of LH peaks ( ± SE/8 h) was also greater (P<.01) for OVX (3.5 ± .3) than sham-OVX gilts (1.7 ± .2). Similarly, the mean concentration of the LH peaks was greater (P<.01) for OVX (4.1 ± .2 ng/ml) than sham-OVX gilts (2.1 ± .2 ng/ml). In Exp. II, mean basal serum LH concentrations, frequency of LH peaks and mean concentration of the LH peaks were similar for all treatments on each day sampled. The frequency of LH peaks ( ± SE/12 h) was greater (P<.05) on d 3 (3.4 ± .3) than on d 5 (2.3 ± .3) and d 7 (2.1 ± .4), but similar to d 14 (2.8 ± .5) in all treatments. In prepuberal gilts, ADX failed to influence serum LH concentration, whereas OVX caused a significant increase in serum LH concentration. We suggest that the ovary is the major steroid-secreting gland having a negative feedback on pituitary gonadotropin production in the prepuberal gilt.

¹ This research was supported by State and Hatch funds allocated to the Georgia Agr. Exp. Sta. The authors wish to thank Dr. Leo E. Reichert, Jr. of the Albany Medical College, Albany, NY, for providing the LH used in the assay system. The authors gratefully acknowledge Dr. T. E. Kiser, Univ. of Georgia, for his advice and support in conducting this research.

² Dept. of Anim. and Dairy Sci., Univ. of Georgia, Athens.

³ Richard B. Russell Research Center, ARS, USDA, Athens.