Serum concentrations of immunoactive and bioactive LH in gilts
Abstract
Three experiments were conducted to determine serum concentrations of immunoactive LH (ILH) and bioactive LH (BLH) in gilts. ILH was determined by radioimmunoassay and BLH was determined by the rat interstitial cell testosterone assay. In the first experiment, two groups of twelve prepubertal gilts were relocated and exposed to boars to stimulate the onset of puberty. Blood samples were taken every 2 h, beginning the third or fifth day after boar exposure, and continued until 24 h after the gilt had exhibited estrus or for 7 d or until 2/3 of the gilts attained puberty. The second experiment was conducted to determine serum concentrations of ILH and BLH during the luteal and follicular phases of the estrous cycle. Blood samples were collected every 20 min for 6 h, then GnRH was injected and blood samples were collected 4 h every 20 min from 16 gilts during the luteal and follicular phases. The third experiment examined serum concentrations of ILH and BLH in 4 groups of 12 gilts at 3, 4, 5 and 6-mo of age. Blood sampling and administration of GnRH was performed as in the second experiment. It was concluded that quantification of ILH in pigs provides a valid estimate of BLH in may physiological situations in gilts including basal as well as spontaneous peaks in prepubertal and cyclic gilts. The following three exceptions were observed in which the biopotency of secreted LH was significantly increased: (1) preovulatory peak of LH in pubertal gilts, (2) GnRH-induced peak of LH during the follicular phase in cyclic gilts, and (3) GnRH-induced peak of LH in 6-month old prepubertal gilts. These observations of increased biopotency all occurred during periods of maximal LH release, and they may reflect the release from the pituitary of stored forms with relatively greater biopotency when the stimulus for release is maximal.
Degree
Ph.D.
Advisors
Diekman, Purdue University.
Subject Area
Anatomy & physiology|Animals
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