Regulation of Serum and Ovarian Relaxin Levels and Corpus Luteum Function During the Second Half of Pregnancy in the Rat (Ovary, Birth, Gestation)

The studies presented in this thesis were conducted to investigate the regulation of relaxin synthesis and secretion by the ovary from days 12 to 20 of pregnancy in the rat (Phase I). Initial immunocytochemical studies utilizing a specific rabbit anti-rat relaxin serum demonstrated that the cells of the corpus luteum (CL) are the only source of relaxin in the pregnant rat. The role of the conceptus in regulating relaxin synthesis and secretion was examined by investigating the effects of conceptus number on serum and ovarian relaxin levels, as well as on serum progesterone (P4) levels and CL weights. A direct relationship between the number of conceptuses and the rate and/or degree of increase in these parameters during Phase I was demonstrated. Additionally, it was shown that the placenta but not the fetus is responsible for maintaining elevated relaxin levels. The influence of the maternal pituitary on CL function during Phase I was then investigated. While rats bearing one conceptus had markedly reduced serum and luteal relaxin levels, serum P4 levels, and CL weights from days 14 to 20 compared to rats bearing a full complement of > 8 conceptuses, hypophysectomy at midpregnancy restored all these parameters except luteal relaxin content to levels similar to those seen in full complement-bearing rats. These results suggest that while the placenta maintains CL function during Phase I, the pituitary has a suppressive effect on the CL. This suppressive effect of the maternal pituitary was further investigated by determining the effects of hypophysectomy on CL function in rats with CL ectopically established under the kidney capsule (eCL) in the absence of the ovary. Consistent with results obtained in rats with intact ovaries, serum relaxin levels and CL weights were lower in eCL rats with 2 conceptuses than in those with > 5 conceptuses, but were significantly increased following hypophysectomy. Serum P4 levels also tended to follow the trends observed with serum relaxin levels. It was concluded that the nonluteal portion of the ovary does not mediate the suppressive effect of the pituitary on luteal function during Phase I in pregnant rats.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physiology

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Golos, Thaddeus Gerard

• Biology, Animal Physiology

Identifier

(UMI)AAI8502153

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/71431