Baboon Corpus Luteum Relaxin: Absence of Effect on Luteal Cell Progesterone Production
Relaxin is a polypeptide hormone with structural similarities, both in amino acid sequence and at the DNA level, to insulin and insulin-like growth factors (1). Until recently it has been recognized to be a hormone of pregnancy; its main function is considered to relate to the preparation of the birth canal prior to parturition. However, Dallenbach and Dallenbach-Hellweg (2) demonstrated its presence using immunofluorescence methods in not only human placenta and decidua but also in the nonpregnant endometrium. Immunohistochemical studies also suggest that the ovary of the cycle as well as of pregnancy may also be a source of relaxin (3, 4, 5). Thus, in the nonpregnant woman, relaxin was identified in the corpus luteum and endometrium in the secretory phase, but not in the proliferative phase. Our data indicates that there is a net production of the hormone into the ovarian vein from an ovary containing the corpus luteum (6). The mean relaxin concentration was 0.41 U ± 0.09 (U ± SE) µg/L (n = 8). In contrast, relaxin was not detectable in the corresponding peripheral plasma or the contralateral venous drainage from an ovary without a corpus luteum. More recently, we have shown that the mid- to late-luteal phase human corpus luteum has a substantial capacity for hormone biosynthesis using DNA/RNA hybridization methodology to assess the presence of relaxin gene transcripts (7). Thus, the objective of the present study was to examine the effect of relaxin on luteal cell progesterone production using baboon (Papio anubis) ovarian tissue.
KeywordsCorpus Luteum Nonpregnant Woman Luteal Cell Progesterone Production Ovarian Vein
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