Plasma steroid, relaxin and dihydro-keto-prostaglandin F-2  changes in the minipig in relation to myometrial electrical and mechanical activity in the pre-partum period

Watts, Alice D.; Flint, A. P. F.; Foxcroft, G. R.; Porter, D. G.

doi:10.1530/jrf.0.0830553

Cited by 31 publications

(21 citation statements)

References 19 publications

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“…In pigs, serum relaxin concentrations are low until 48 h before birth. During this antepartum period, plasma concentrations of relaxin increase rapidly to reach a peak 14 h before parturition and then decline rapidly to the time of delivery (Sherwood et al, 1975;Watts et al, 1988). The increased relaxin concentrations observed just before parturition may synergize with oestrogen to prevent premature stimulation of uterine contractions by oxytocin and prostaglandins.…”

Section: During Pregnancy and Parturitionmentioning

confidence: 99%

Action of relaxin on uterine contractions - a review

Downing

Hollingsworth²

1993

Reproduction

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Relaxin is a potent, reversible inhibitor of spontaneous uterine contractions in a number of species, including rats, mice, gui nea\x=req-\ pigs, rabbits, sheep and pigs, in vivo and in vitro. The potency of relaxin on the isolated uterus is about 1\p=n-\5nmol l \m=-\1 (assuming a molecular mass of 6 kDa; Table 1); relaxin is therefore one of the most potent uterine relaxants known. The isolated human uterus, however, has been reported to be relatively insensitive to relaxin. Human recombinant relaxin has only recently become available and, therefore, in this review it may be assumed that the studies described were conducted using porcine relaxin unless stated otherwise. Low doses of relaxin selectively reduce the frequency of contractions in rats in vivo and at high doses complete inhibition of myometrial contractions is achieved Hollingsworth, 1991, 1992a). The duration of inhibition is related to the dose of relaxin administered. Relaxin has a rapid onset of action in vivo (within 1-2 min of adminis¬ tration of an intravenous dose) and recovery of uterine contrac¬ tions to control values occurs rapidly after clearance of relaxin from the circulation. The half-life of endogenous relaxin in the circulation of the mid-and late-pregnant rat is 80 and 50 min, respectively (Sherwood el al., 1984) and human relaxin shows half-lifes of 15 and 60 min for the second and third decay phases in the rat, respectively (Cossum et al., 1992). Similarly, in vitro, uterine contractions are inhibited rapidly upon addition of relaxin to the tissue bath (Wiqvist and Paul, 1958; Bradshaw et al., 1981; Anderson, 1984), and recovery of uterine contractions occurs after relaxin is washed from the bathing medium. Collectively these observations suggest that relaxin inter¬ acts with a plasma membrane receptor in the myometrium.

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Section: During Pregnancy and Parturitionmentioning

confidence: 99%

Action of relaxin on uterine contractions - a review

Downing

Hollingsworth²

1993

Reproduction

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“…Relaxin inhibits myometrial contractions in sows (Watts et al, 1988) and high titres in the immediate pre-farrowing period might be sufficient to slow the progress of delivery. This would differ from the rat because, although continuous infusions of porcine relaxin prolonged pregnancy in rats, deliveries that occurred after infusions were stopped were accomplished significantly faster than normal (Jones & Summerlee, 1986b).…”

Section: Discussionmentioning

confidence: 99%

Lack of effect of relaxin on oxytocin output from the porcine neural lobe in vitro or in lactating sows in vivo

Porter

Ryan²,

Norman³

1992

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Oxytocin was measured in incubates and perifusates of neurosecretosomes prepared from sow neural lobes (n = 50) and in incubates of isolated neural lobes (n = 5). In none of these preparations was oxytocin output affected by exposure to purified porcine relaxin (at concentrations up to 10(-7) mol l-1). Moreover, in lactating sows (n = 9), 6-10 days post partum, the administration of porcine relaxin (1.5 or 3.0 mg) intravenously, immediately before a suckling episode, did not affect the plasma oxytocin profile compared with saline treatments (within sow) nor did it alter suckling behaviour or the weight gain of the litter. In all sows, a spike (25-75 pg ml-1) of oxytocin was measured during milk ejection coincident with suckling. These results suggest that porcine relaxin does not affect oxytocin release in suckling sows in contrast to reported findings in rats. The data also support the view that porcine relaxin could be used at farrowing without adverse effects on suckling.

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“…Its significance can only be understood if the various effects of relaxin are taken into account, i.e. increased cervical distensibility [22], electrical activity inhibition in the myometrium [23] and prevention of the central oxytocin release [24], Reduction of circulating relaxin could be a prerequisite for entering into active labor [25],…”

Section: Discussionmentioning

confidence: 99%

Changes of Relaxin Concentrations Determined by Immunodensitometry in Ovaries of NMRI Mice during Pregnancy

Psalti

Rahier²,

Loumaye

et al. 1990

Gynecol Obstet Invest

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Relaxin has been localized in corpora lutea (CL) of pregnant NMRI mice using the avidin-biotin complex immunocytochemical procedure and an antiserum against highly purified porcine relaxin. The immunostaining was measured by immunodensitometry. Relaxin immunostaining was first observed in luteal cells of type I gestational CL on day 11.5 (D_11.5), For each investigated day, all CL were identically stained, and immunostaining was evenly dispersed all over the CL. Seventy-five percent of cells were stained at D_11.5, and nearly all cells were stained betweeen D_13.5 and D_18.5. The staining intensity increased throughout the last half of pregnancy, reaching a maximum at Dig. A few hours before parturition, at D_18.5, relaxin immunostaining decreased dramatically and reached the background level shortly after delivery. From our results we may conclude that, in murine CL, the number of relaxin-secreting cells and the intracellular storage of the peptide increase during pregnancy. The disappearance of relaxin with the cells occurs rapidly ± 12 h before parturition.

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Plasma steroid, relaxin and dihydro-keto-prostaglandin F-2 changes in the minipig in relation to myometrial electrical and mechanical activity in the pre-partum period

Cited by 31 publications

References 19 publications

Action of relaxin on uterine contractions - a review

Action of relaxin on uterine contractions - a review

Lack of effect of relaxin on oxytocin output from the porcine neural lobe in vitro or in lactating sows in vivo

Changes of Relaxin Concentrations Determined by Immunodensitometry in Ovaries of NMRI Mice during Pregnancy

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