On the Structure and Function of Relaxin

Abstract

The endocrinological events leading to parturition are poorly understood. There are obvious species differences and no generalizations are possible at this time. In 1926 Hisaw called attention to the fact that in some mammals an ovarian factor is produced that leads to an enlargement of the birth canal in preparation for parturition. Subsequent work showed that this factor suppressed uterine contractions that might be harmful to the fetus. Hisaw and his coworkers also demonstrated that this ovarian factor was not a steroid but a protein susceptible to proteolytic action. He determined some physical properties of his new factor, relaxin, and compared them in an almost visionary fashion with the properties of insulin. Importantly, the involvement in parturition of a distinct hormone was demonstrated for the first time. The next thirty years of relaxin research was dominated by studies concerning the physiology of relaxin. The investigation of the biochemistry of relaxin suffered from the absence of an accurate and convenient bioassay. In 1930 Fevold et al. introduced the guinea pig assay which was rather elaborate and not sufficiently objective. The introduction of the mouse assay system by Steinetz et al. (1959) and the discovery of Kliman and Greep (1958) that the activity of relaxin in mice could be enhanced more than 100-fold by simultaneous injection of an adjuvant provided a better basis for the purification of relaxin.