RELAXIN AND ESTROGEN SYNERGISTICALLY ACCELERATE GROWTH AND DEVELOPMENT IN THE UTERINE CERVIX OF PREPUBERTAL PIGS

This study was designed to determine the developmental and growth-prom oting effects of relaxin with or without estrogen on the uterine cervi x of prepubertal gilts. Twenty littermate gilts of similar body weight (33 +/- 3 kg; mean +/- SE) at 80 days of age were randomly assigned t o four treatments: Vehicle (Control, 1 mi PBS and 1 mi vegetable oil, n = 5); Relaxin (Relaxin, in PBS, 1 ml, 167 mu g ml(-1), n = 5); Estra diol Benzoate (EB, in vegetable oil, 1 mi, 2 mg ml(-1), n = 5); and Re laxin plus EB (Relaxin + EB, at the same doses, n = 5), total six intr amuscular injections for all treatments. Twenty four hours after the l ast injection, hysterectomy was performed, and the uterine tissues wer e immediately frozen at -80 degrees C. Samples were taken from the mid dle portions of the cervix and the uterine hems and dried to a constan t weight to determine the dry weight and water concentration. Homogena tes of uterine hems and cervices were analyzed for concentrations and contents of protein, hydroxyproline (collagen index) and DNA. Relaxin alone had no significant effect on any parameters (i.e., wet weight, R elaxin vs, Control: 36 +/- 5 vs, 28 +/- 3 g uterus(-1), dry weight 5.6 +/- 0.6 vs. 4.4 +/- 0.4 g uterus(-1)). EB alone increased significant ly (P < 0.05) wet weight of the uterus (EB vs. Control: 85 +/- 23 vs. 28 +/- 3 g uterus(-1)), dry weight (EB vs. Control: 14.5 +/- 3 vs. 4.4 +/- 0.4 g uterus-l), and hydroxyproline content (EB us. Control: 47.2 +/- 13 vs. 12.6 +/- 4 mg cervix(-1)). In the presence of EB, relaxin treatment increased all measurements compared with Control (i.e., wet weight, Relaxin + EB vs. EB: 136 +/- 34 vs. 28 +/- 3 g uterus(-1)). Co mpared with EB, Relaxin + EB significantly (P < 0.05) increased the ut erine wet weight (Relaxin + EB vs. EB: 136 +/- 34 vs. 85 +/- 23 g uter us(-1)), the hydroxyproline content (Relaxin + EB vs. EB: 91 +/- 29 vs . 47 +/- 13 mg cervix(-1)), and DNA content (Relaxin + EB vs. EB: 8.1 +/- 2 vs. 5.4 +/- 1 mg cervix(-1)). These results indicate that the gr owth-promoting effects of relaxin on the uterus and cervix may bet at least partly, estrogen-dependent and that the growth and development o f the uterus and cervix can be accelerated by a combination of relaxin and estrogen treatment.