In Vitro Inhibition of Spontaneous Contractions of the Rat Uterus by Relaxin-Containing Extracts of Sow Ovaries

Abstract

Extracts of sow ovaries inhibit the spontaneous contractions of excised rat uteri suspended in Locke''s soln. Relaxin prepns. from pregnant sow ovaries can suppress motility in doses as small as 0.0033 [mu]g./ml. This effect is not due to contamination with histamine or epinephrine. The effect on the rat uterus is proportional to the relaxin content of these extracts as detd. by the guinea pig symphysis pubis assay method. Both effects are diminished by reduction, methylation or formylation but not by acetylation or deamination. Relaxin preparations do not produce significant inhibition of the uterine response to pitocin or acetylcholine, but do increase the threshold to electrical stimulation.