Effect of Porcine Relaxin on Cervical Dilatation, Pelvic Area and Parturition in Beef Heifers1

Abstract

Purified porcine relaxin (3,000 U/mg) was administered either into the cervical os or by intra-muscular injection to crossbred beef heifers beginning 4 days before expected parturition, in an attempt to elucidate the physiological roles of relaxin in cervical dilatation, the pelvic area, and parturition. Relaxin (3,000 U in a gel vehicle), when administered into the cervical os during late pregnancy, induced significant dilatation of the cervix 8 and 16 h later, as compared to vehicle-treated controls. This induced cervical dilatation did not cause premature parturition in relaxin-treated heifers and was similar to controls. Exogenous relaxin during late gestation elicited an increased growth rate of the pelvic area, as determined by sequential measurements of height and width of the pelvic canal. These results indicate that, before parturition, pelvic width increased more rapidly than pelvic height and that exogenous relaxin elicited a greater response in both parameters. Highly significant nocturnal elevations in concentrations of progesterone in peripheral blood serum occurred in vehicle-treated control heifers during late pregnancy. These nocturnal elevations in serum levels of progesterone were significantly reduced after 8 and 16 h of relaxin treatment in experimental animals as compared to control heifers. The mechanisms by which porcine relaxin reduces ovarian progesterone secretion in beef heifers remain undefined.

Relaxin on Induction of Parturition in Beef Heifers*

“…Pelvic area increases gradually in cattle throughout gestation, then the rate increases during the last 4 days preceding normal parturition, which coincides with increasing blood concentrations of 17/3-estradiol (17jS-E 2 ) and estrone (Ei) (15)(16)(17)(18)(19)(20). Administration of porcine relaxin increases both pelvic area and cervical dilatation in beef heifers during late pregnancy (21,22). The objectives of this study were to determine the effects of intracervical administration of purified porcine relaxin during late gestation in cattle on the induction of parturition, cervical dilatation, and pelvic relaxation as well as plasma concentrations of Ei, 17jft-E 2 , and progesterone.…”

Hormonal control of late pregnancy and parturition in beef cattle and pigs

“…Studies conducted to examine the effects of highly purified relaxin in pregnant animals have shown that relaxin stimulates growth and softening of the cervix in pigs and rats (Downing and Sherwood, 1985). Similar properties of relaxin were observed in cattle (Perezgrovas and Anderson, 1982;Musah et al, 1988), in these studies relaxin administration during late pregnancy promoted increased pelvic area and facilitated earlier calving in treated animals compared with untreated controls. reported that relaxin has growth-promoting properties on the cervix during late pregnancy.…”

The Preliminary Study About the Involvement of Relaxine in Adverse Effect of Polychlorinated Biphenyls on Bovine Myometrial Contractions

“…Moreover, RLX induced suppression of OT release from corpus luteum in cow [28]. Bovine corpora lutea from late pregnancy contain active RLX, while there is markedly lower than in swine [29]. Since it was found previously that PCBs increased amount of stimulators of contractions (OT and PGF2), here it was hypothesized that PCBs can increase the uterine The aim of this study was to investigate the effect of PCB 77 and PCB 153 on myometrial reception of RLX signal during pregnancy, and therefore on (a) mRNA expression of receptor of RLX and (b) RLX-inhibition of myometrial strips contractions.…”

“…While to study the inhibition of contractions, there were used two type of RLX. It was porcine RLX (30, 60 and 100 ng/ml, according to Kaczmarek et al [32], it is 200-500 ng/ml) since it was also used in study in beef heifers in vivo [29,33]. Since signaling by Relaxin-2 human through its target receptors enhances the growth of pubic ligaments and ripening of the cervix during birth [34] it was also used in this study (10-400 ng/ ml).…”