Bioassay methods for relaxin: uses and pitfalls.

Abstract

The ability of aqueous extracts of porcine corpora lutea of pregnancy to “relax” the pubic symphysis of the estrogen-primed ovariectomized guinea pig was first described by Hisaw (1926). Subsequent work showed that porcine luteal extracts which contained guinea pig pubic symphysis-relaxing activity could inhibit contractions of uterine myometrium of rats in vitro (Sawyer et al. 1953) and guinea pigs in vivo (Krantz et al.3 1950). Around the same time, it was reported that crude extracts of sow corpora lutea induced interpubic ligament formation in estrogen primed mice (Hall and Newton, 1946; Kliman et al. 3 1953). These basic observations led to the development of numerous bioassay methods for relaxin which have been amply documented in previous reviews (Frieden and Hisaw, 1953; Hall, 1960; Steinetz et al. 1969). The present paper will, therefore, be devoted primarily to a discussion of the uses (and abuses!) of the various assay methods, the pitfalls which may be encountered in assaying relaxin activity in impure extracts and the growing realization that relaxin activity may be associated with a family of related polypeptides. Of special interest are recent observations which suggest that relaxin-like hormones obtained from different species may not be equally effective in the classical bioassay methods.