Myometrial Activity and the Distribution of Blastocysts in the Uterus of the Rat: Interference by Relaxin

Publisher Website
Google Scholar
Abstract
Intravenous infusion of porcine relaxin (1700 h on Day 4 to 0900 h on Day 5), during the period when blastocysts are transported into and throughout the uterine horn in rats, disorganized the even distribution of ova among cranial, mid, and caudal thirds of the uterus normally seen on the morning of Day 5. This appeared to be due to inhibition of the myometrium rather than to an interference in other postulated mechanisms of spacing, because after cessation of the relaxin infusion at 0900 h (Day 5) the blastocysts were redistributed uniformly among the thirds of the uterus before implantation (p.m., Day 5). These data provide evidence that the propulsion of blastocysts through the uterus in the rat at least initially is accomplished by myometrial activity.