Effects of relaxin administration in early gestation or prior to mating on uterine length and fetal survival in gilts

Abstract

The objective of this research was to determine the effect of administration of porcine relaxin to gilts during early gestation, or during the follicular phase of the estrous cycle immediately preceding mating, on the length of the uterus and consequently the number of surviving fetuses. Experiment 1 determined the individual and combined effects of 10 days of administration of relaxin (0.5 mg, 4 times daily), estradiol benzoate (1 mg, 2 times daily), and progesterone (50 mg, 2 times daily) on uterine wet weight and length in 58 ovariectomized 8-mo-old pubertal gilts. Relaxin alone had no effect on either uterine length or wet weight. Estrogen increased uterine wet weight, and this effect was augmented by relaxin. Progesterone increased uterine length, and this effect was augmented by estrogen. Combined treatment with progesterone, estrogen, and relaxin increased both uterine length and wet weight maximally. Experiment 2 determined the effects of relaxin administration in early gestation or prior to mating on uterine length and fetal survival in 75 unilaterally ovariectomized-hysterectomized gilts. Relaxin (0.5 mg, 4 times daily) was administered during three treatment periods, and uteri were collected on Day 40 of gestation. In this study, relaxin administration from Days 11 to 20 of gestation reduced the number of live fetuses (p = 0.01) and percentage survival (p = 0.01) and resulted in shorter uterine length (p = 0.01) and lower uterine wet weight (p = 0.03) than in controls, but did not affect length of uterus or uterine dry weight. Relaxin administration from Days 22 to 31 of gestation did not influence fetal survival, uterine length, uterine length per fetus, uterine wet weight, or uterine dry weight.(ABSTRACT TRUNCATED AT 250 WORDS)

Uterotrophic effects of relaxin related to age and estrogen receptor activation in neonatal pigs

“…Similar relationships were described for the pig (Hall et al 1990, Galvin et al 1991, Ohleth et al 1997. Additionally, data generated in ovariectomized, pubertal gilts (Zaleski et al 1995) indicating that ten days of relaxin treatment failed to promote uterine growth in the absence of ovarian steroids (estrogen or progesterone), support the view that uterotrophic actions of relaxin are at least facilitated by steroid hormone receptor Uterotrophic effects of relaxin are estrogen receptor-dependent 947 activation. Studies involving the MCF-7 breast cancer cell line showed that relaxin could stimulate expression of an estrogen response element-luciferase reporter gene (Koos & Pillai 2001), indicating that signaling pathways affected by relaxin can also activate the ER in the absence of estrogen.…”

Relaxin Family Peptides and Their Receptors

“…In nonpregnant rats, the effect of relaxin on the growth and development of the uterus is associated with vascular dilatation (547) and in rhesus and marmoset monkeys with endometrial angiogenesis (145,185). In primates and rats, pretreatment with estrogens enhances the effects of relaxin (1,145), and in pigs, estrogens are obligatory for the growth-promoting effects of relaxin (242,581). The mechanism involved in the interaction between relaxin and estrogen is not well understood, although in rats estrogen pretreatment dramatically increases relaxin receptor binding sites in the uterus (400,401,515).…”

Ο Ρόλος Της Ρελαξίνης Στις Αγγειακές Παθήσεις

“…Η ρελαξίνη επηρεάζει τη συσταλτικότητα της μήτρας [482] και την ανάπτυξη της μήτρας [483] κατά τη διάρκεια της κύησης στους μύες, τους επίμυες το ινδικό χοιρίδιο και τους χοίρους, αλλά έχει μικρή επίδραση στην ανθρώπινη μήτρα [484,485] . Σε επίμυες που δεν βρίσκονται σε κύηση, η ρελαξίνη επηρεάζει τη, ανάπτυξη της μήτρας μέσω της αγγειοδιαστολής [486] και τόσο στους επίμυες, όσο και στους χοίρους και σε πρωτεύοντα ζώα, η δράση της ενισχύεται από την παρουσία οιστρογόνων [487][488][489][490] , αν και οι μηχανισμοί αλληλεπίδρασης της ρελαξίνης με τα οιστρογόνα δεν είναι καλά κατανοητοί. Η δράση αυτή της ρελαξίνης στη μήτρα δεν φαίνεται να είναι σημαντική για άλλα ζώα εκτός από τον χοίρο [491] , ενώ στον άνθρωπο πιθανότατα επηρεάζει μόνο τη διαδικασία της εμφύτευσης του ζυγώτη και όχι τα επόμενα στάδια της κύησης.…”