In vitro analysis of antisera to relaxin

This article describes the development of an in vitro assay to quantitate the ability of antisera to inhibit the biological action of the pregnancy hormone, relaxin. The procedure employed a modification of the in vitro assay for the ability of relaxin to inhibit spontaneous uterine contractions as initially described by Kroc et al. (1959). Several antisera were tested that showed inhibition of relaxin activity. Tests of cross-reactivity demonstrated that antiserum produced against porcine relaxin effectively inhibited the activity in relaxin preparations from cows and rabbits but was much less effective in inhibiting the activity in rat relaxin preparations. Agar double-immunodiffusion studies supported the cross-reactivity studies in that cow and rabbit relaxin preparations gave reactions of identity with the porcine relaxin while the rat relaxin preparation did not produce a precipitin line with the anti-porcine relaxin antiserum.