Local relaxin biosynthesis in the ovary and uterus through the oestrous cycle and early pregnancy in the female marmoset monkey (Callithrix jacchus)

The pattern of peripheral serum concentration for the peptide hormone relaxin in women points to the possibility of an interesting paracrine function in the cycle and early pregnancy. In order to investigate this physiology in detail, it was decided to examine local relaxin biosynthesis in an established primate model for human female reproductive function, the marmoset monkey (Callithrix jacchus). In this initial study relaxin biosynthesis was assessed using a combination of molecular and immunological techniques through the oestrous cycle in the marmoset monkey. The nucleotide sequence of the full-length relaxin gene transcript was cloned from the marmoset ovary and found to be closely homologous to that of the human H2 relaxin. Using gene specific probes derived from this sequence, RNase protection assays, reverse transcription-polymerase chain reaction (RT-PCR) assays and in-situ hybridization, showed relaxin gene expression within the ovary in theca cells and corpora lutea in the oestrous cycle, increasing in early pregnancy. Relaxin gene expression was also identified at a low level in the uterus and placenta, and at a higher level in the prostate in the male marmoset monkey. Using two different relaxin-specific antisera, relaxin-like immunoreactivity was observed in the ovary with a pattern of distribution coincident with that obtained by in-situ hybridization. Immunoreactivity was also found in the nonpregnant uterus, within the endometrial epithelium of the late proliferative phase and increasing within the glands through the secretory phase. Taken together, the pattern of relaxin peptide and mRNA expression show there is the basis for local relaxin physiology within the ovarian follicle and corpus luteum, and within the uterus during the oestrous cycle in this new world monkey.