Influence of Ovarian Steroids on Relaxin-Induced Distensibility and Compositional Changes in the Porcine Cervix1

A study was conducted to examine the influence of ovarian steroids on relaxin-induced changes in distensibility and composition of the uterine cervix in gilts. Ovariectomized, prepubertal gilts received (i.m.) either 1) 0.5 ml corn oil (CO) for 16 days; 2) 0.5 ml CO for 16 days and estradiol benzoate (EB; 200 micrograms) twice daily on Days 13-14; 3) EB on Days 0-1 followed by CO on Days 3-16 (EB + CO); 4) EB on Days 0-1 followed by CO on Day 2 and twice daily injections of 100 mg progesterone (P) on Days 3-16 (EB + P); or 5) EB on Days 0-1 followed by CO on Day 2 and P on Days 3-16 with additional EB treatment on Days 13-14 (EB + P + EB). One half of each group also received (i.m.) 0.5 ml 0.1 M PBS or 0.5 mg relaxin (RLX) every 6 h for 54 h coinciding with the final 2 days of the experimental period. Administration of RLX increased (p < 0.05) cervical distensibility compared to PBS treatment, with the response being greater (p < 0.05) in EB-, EB + CO-, and EB + P + EB-treated gilts compared to CO- or EB + P-treated gilts. Water content of cervical tissue was greater (p < 0.05) in EB-, EB+P- and EB + P + EB-treated gilts compared to CO- or EB + CO-treated gilt: and in all treatments, RLX enhanced (p < 0.05) imbibition of water by cervical tissues compared to that in PBS-treated gilts.(ABSTRACT TRUNCATED AT 250 WORDS)