Human Relaxins: Chemistry and Biology*

IT IS more than a decade since the previous and first review in this journal on relaxin (1). There have been many significant advances over this period which have been reviewed by us and others (2–4). The sequencing of the two human relaxin genes termed HI and H2 relaxins, and the availability of these peptides and antibodies have allowed relatively rapid progress in knowledge over the last few years. There is enough accumulated data to warrant specialization within the field and to allow us to focus this review on the human relaxins. Where there are gaps in the knowledge of effects of human relaxin in human systems, they have been filled with data from nonhuman animal experimentation to provide a more complete picture of the status of the field. A summary of the principal advances over the period 1983–1992 is presented in Table 1. Over this period the sequences of the two human relaxin genes as well as their tissue expression were described together with the chemical and recombinant syntheses of their peptides, the development of an homologous RIA, and a method of labeling relaxin with 32P while retaining its biological activity for receptor detection.