Expression of the relaxin gene in rat tissues

The peptide hormone relaxin is produced at high levels in the corpus luteum of the rat ovary during pregnancy. The biological effects of the hormone include remodelling of collagen in target tissues such as the cervix, and inhibition of uterine contractility. In addition, many paracrine actions for the hormone have been proposed, however sites of relaxin production outside the ovary have not been well characterized. We have investigated relaxin gene expression in a range of rat tissues using the techniques of reverse transcription/polymerase chain reaction (RT/PCR), RNase protection and immunohistochemistry. Relaxin mRNA was detected by RT/PCR in brain, uterus, prostate gland, pancreas and kidney, with other tissues giving weak signals. Relaxin gene expression in brain was detected by RNase protection, and relaxin-like immunoreactivity was observed in the arcuate nucleus of the hypothalamus of rat brain. This characterization of sites of relaxin gene expression provides further evidence for proposed paracrine actions of relaxin which may be important in non-pregnant and male rats in addition to the pregnant female.