Changes in Circulating Relaxin Levels during Pregnancy and Early Lactation in Japanese Monkeys (Macaca fuscata fuscata).

Abstract

Abstract. Changes in relaxin concentrations in plasma throughout pregnancy and early lactation up to one month after parturition were characterized in 10 Japanese monkeys by a heterologous radioimmunoassay (RIA) based on the porcine RIA. Plasma levels of LH/monkey chorionic gonadotropin (mCG), estradiol-17β, progesterone and immunoreactive (ir-) inhibin were also monitored for the entire period. Relaxin levels in the plasma were low before conception. An accelerated rise in plasma relaxin levels was found during pregnancy. The first increase was noted during early pregnancy, with a peak (267.5 ± 50.5 pg/ml) at Day 31 ± 2.4 of pregnancy (Day 0= day of LH surge). The second increase was noted just before term with a peak (235.6 ± 37.5 pg/ml). After parturition, relaxin levels in the plasma abruptly declined but were maintained at approximately 100 ng/ml during early lactation. The first rise in plasma relaxin during pregnancy was in parallel with rises of mCG and progesterone, and the second rises was well correlated with those of plasma estradiol-17β ,progesterone and ir-inhibin. These results suggest that the major source of relaxin is corpus luteum and placenta during pregnancy in Japanese monkeys. Key words: Relaxin, Japanese monkey, Pregnancy, Parturition, Lactation (J. Reprod. Dev. 48: [383][384][385][386][387][388][389][390][391] 2002) elaxin is a polypeptide hormone found in the serum of pregnant mammals [1], and is known to assist the maintenance of pregnancy and the preparation of the reproductive tract for parturition in mammalian species [1]. Furthermore, it has been reported that relaxin is involved in the growth of the mammary gland during pregnancy, at the onset of lactation, and in established lactation [2]. , immunoreactive relaxin rises to a peak shortly before parturition and is correlated with the increase in cervical dilatability and formation of an interpubic ligament. In women, relaxin is detectable from the time of missed menses, is highest in the first trimester, and gradually declines thereafter until delivery, without a prelabor surge

Annual ovarian activity monitored by the noninvasive measurement of fecal concentrations of progesterone and 17β-estradiol metabolites in rusa deer (<i>Rusa timorensis</i>)

“…On the other hand, fecal concentration of 17β-estradiol began to increase in the late pregnancy, remained elevated at the day of parturition and then decreased to the baseline level in the lactating period. In mammals, estrogens were increase during pregnancy, especially in late pregnancy, such as domestic ungulates (mares [15] and goats [12]), laboratory rodents (rats [25] and golden hamster [17]) or wild mammals (Japanese monkeys [16, 23], red deer [2], white-tail deer [10] and reindeer [20]). High levels of circulating estrogens promote production of oxytocin receptor [34] and relaxin receptor [6] to assist preparation of the reproductive tract for parturition and subsequently lactation.…”

Effects of Prostaglandin E2 on Ripening of the Cervix and Secretion of Relaxin, Luteinizing Hormone (LH), Estradiol-17.BETA. and Progesterone at Term Pregnancy in the Japanese Monkey (Macaca fuscata fuscata).

“…Our previous paper [5] suggested that the major source of circulating relaxin in pregnant Japanese monkeys may be the ovary, probably the corpus luteum, as in women and phesus monkeys [4,8,14]. Relaxin-containing cells have been shown immunocytochemically in the luteal cells of human term ovary [15].…”

“…W e h a v e r e c e n t l y determined plasma relaxin levels throughout pregnancy in the Japanese monkey [5]. With spontaneous parturition, a rise in plasma relaxin levels has been detected toward term [1,5].…”

“…W e h a v e r e c e n t l y determined plasma relaxin levels throughout pregnancy in the Japanese monkey [5]. With spontaneous parturition, a rise in plasma relaxin levels has been detected toward term [1,5]. Our results [1] in conjunction with another study [6] that reports results for pregnant women infused with either oxytocin or PGF2α fail to show any changes in plasma relaxin levels made it of interest to determine whether cervical dilatation induced by PGE2 is associated with relaxin change or not.…”

The Macaque Placenta—A Mini-Review

“…Relaxin acts synergistically with progesterone in maintaining pregnancy and enables the relaxation of the pelvic ligaments to aid in parturition. In the macaque, relaxin is produced by both the corpus luteum and the placenta (Shimizu et al 2002).…”