Regulation of Antepartum Relaxin Release in the Pregnant Rat: Role of the Maternal Pituitary Gland, Luteinizing Hormone and Prostaglandins
Gordon, Wayne Lecky
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https://hdl.handle.net/2142/71415
Description
Title
Regulation of Antepartum Relaxin Release in the Pregnant Rat: Role of the Maternal Pituitary Gland, Luteinizing Hormone and Prostaglandins
Author(s)
Gordon, Wayne Lecky
Issue Date
1982
Department of Study
Physiology and Biophysics
Discipline
Physiology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Animal Physiology
Abstract
The regulation of the antepartum elevation and decline of serum relaxin levels in the pregnant rat is poorly understood, but may be related to functional luteolysis (Endocrinology 107:671, 1980). Factors which served as a beginning for the investigation of the regulation of antepartum relaxin release were those which have been implicated in luteolysis; these are the maternal pituitary, luteinizing hormone (LH) and prostaglandin (PG) F(,2(alpha)).
Ablation of the maternal pituitary (HYPOX rats) on the fourteenth day of pregnancy (Day 14) delayed the onset of birth and prolonged delivery as well as protracted luteolysis and delayed the antepartum elevation and decline of serum relaxin levels.
Preliminary experiments indicated that iv injection of LH, but not follicle-stimulating hormone (FSH) or prolactin, or multiple injections of gonadotropin-releasing hormone on Day 20, the day prior to the normal antepartum elevation in serum relaxin, resulted in a rapid elevation in serum relaxin levels. The Sprague-Dawley rats used in this study normally give birth on Day 22 (DAY 22 RATS) or 23 (DAY 23 RATS). Additionally, the antepartum decline in serum relaxin and progesterone to low levels occurs earlier in DAY 22 RATS than in DAY 23 RATS. Sustained administration of LH resulted in birth and the time of decline of antepartum levels of both relaxin and progesterone which were similar to those of DAY 22 RATS. Administration of LH antiserum to intact rats from Day 19 through Day 22 delayed birth and the time of decline of antepartum levels of both relaxin and progesterone.
Intravenous injection of PGF(,2(alpha))-tromethamine salt to intact rats on Day 20 resulted in a rapid elevation of serum relaxin levels. Administration of the prostaglandin synthesis inhibitor indomethacin to inact rats from Day 19 through Day 20 delayed or prevented birth, delayed the antepartum elevation of serum relaxin levels until after Day 23 and protracted luteolysis.
The results of these experiments indicate that maternal pituitary LH and prostaglandins may regulate the normal progression of birth, antepartum relaxin levels and luteolysis.
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