Uterotropic actions of relaxin in prepubertal gilts.

Uterotropic actions of relaxin (RLX) have been demonstrated in rats and mice but not in other species. Experiments were conducted to assess (1) if RLX has uterotropic effects in prepubertal gilts and (2) if RLX-induced imbibition of water by uterine tissues is mediated by histamine. Prepubertal gilts received (i.m.) either 0.5 mg pRLX (greater than or equal to 3000 U/mg; n = 10) in 0.1 M phosphate-buffered saline (PBS) or PBS vehicle (n = 8) every 6 h for 54 h. Additionally, one-half of each group received either (1) the histamine receptor antagonists (300 mg i.m. of each), pyrilamine maleate (H1) and cimetidine (H2), in PBS and corn oil, respectively, or (2) control vehicles every 6 h for 66 h beginning 12 h prior to initiation of RLX treatment. Treatment with RLX stimulated a twofold increase (p less than or equal to 0.05) in uterine weight in prepubertal gilts. Increases in total uterine weight were manifested by greater (p less than or equal to 0.05) uterine water content and dry weight in RLX-treated gilts. Cotreatment with histamine receptor antagonists did not alter RLX-induced changes in uterine water content or dry weight. Uterine contents of soluble protein and DNA were greater (p less than or equal to 0.05) in RLX-treated gilts compared to controls. Treatment with RLX tended (p approximately 0.08) to reduce protein; DNA ratio of uterine tissues and increased (p less than or equal to 0.05) uterine DNA as a percentage of uterine dry weight.(ABSTRACT TRUNCATED AT 250 WORDS)