Endocrinology, Vol 114, 364-368, Copyright © 1984 by Endocrine Society

ARTICLES

Bioassay of porcine relaxin components by in vitro inhibition of rat uterine contractions

MB Anderson

Isolation of porcine relaxin by the procedure of Sherwood and O'Byrne has resulted in three, slightly different relaxin molecules which differ in the length of their B chains. The purpose of this study was to determine if a difference in biological activity exists among the three relaxin forms as determined by the in vitro inhibition of spontaneous rat uterine contractions. Uterine segments from estrogen- primed, virgin rats were suspended in Locke's solution in a siliconized, water-jacketed organ bath at 37 C. After regular contractions were established, the minimum concentration of each relaxin component necessary to cause total inhibition was determined. Total inhibition for all three relaxin components was obtained at a chamber concentration of 0.2-0.36 U/ml. Thus, no difference in biological activity exists among the three relaxin forms as demonstrated by the rat uterine inhibition bioassay.