Changes in kinetic properties of oxytocin receptors in longitudinal muscle membranes of rat uterus during gestation

Kaneko, Yuji; Kawarabayashi, Tatsuhiko; Sugimori, Hajime; Tsukamoto, Takuji

doi:10.1002/jmr.300080303

Cited by 11 publications

(4 citation statements)

References 28 publications

(19 reference statements)

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“…The EC 50 values of the first phase was 3.1 AE 0.9 nM (Fig. 2), a value which correspondents well with the K d value obtained from [ 3 H]oxytocin binding experiments (Kaneko et al, 1995).…”

Section: Resultssupporting

confidence: 86%

“…Over the course of gestation, myometrial contraction capacity increases several fold (Osa and Katase, 1979), the content of myosin light chain (MLC) and calmodulin become significantly increased (Matsui et al, 1986), and both the membrane density of oxytocin receptors and their affinity for ligand are significantly increased (Soloff et al, 1979;Fuch et al, 1992;Shojo and Kaneko, 2000). Furthermore, the dynamic properties of oxytocin receptors in myometrial muscle apparently change at term (Kaneko et al, 1995). Oxytocin-induced myometrial contraction is associated with an increase in intracellular free Ca 2 ([Ca 2 ] i ) that leads to MLC phosphorylation (Olins and Bremel, 1984).…”

Section: Introductionmentioning

confidence: 99%

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Oxytocin‐induced phosphorylation of myosin light chain is mediated by extracellular calcium influx in pregnant rat myometrium

Shojo¹,

Kaneko

2001

J of Molecular Recognition

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Studies of oxytocin-induced phosphorylation of myosin light chain (MLC), resulting in myometrial contraction, suggest that extracellular Ca(2+) influx is involved in its signal transduction. To explore the possibility that intracellular Ca(2+) mobilization by oxytocin may also contribute to MLC phosphorylation, we investigated the relative contributions of these Ca(2+) sources to oxytocin signal transduction in myometrium of pregnant rat. In pregnant rat myometrium, oxytocin-induced Ca(2+) influx occurs via an L-type voltage-dependent Ca(2+) channel. Treatment with verapamil, an antagonist specific for these channels, significantly diminished MLC phosphorylation observed in response to oxytocin administration without affecting the release of Ca(2+) from intracellular Ca(2+) stores. Furthermore, oxytocin-induced MLC phosphorylation was not observed when extracellular Ca(2+) was not present. Our results clearly indicate that extracellular Ca(2+) influx, rather than release from Ca(2+) storage sites, is essential for oxytocin-induced MLC phosphorylation.

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“…The EC 50 values of the first phase was 3.1 AE 0.9 nM (Fig. 2), a value which correspondents well with the K d value obtained from [ 3 H]oxytocin binding experiments (Kaneko et al, 1995).…”

Section: Resultssupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Oxytocin‐induced phosphorylation of myosin light chain is mediated by extracellular calcium influx in pregnant rat myometrium

Shojo¹,

Kaneko

2001

J of Molecular Recognition

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“…2. the expression of OT receptors. Certainly, the increase in OT receptors in the myometrium preceding parturition and during labor (1,48,67), including in the rabbit (62), demonstrates that such rapid, short-term changes can occur. However, a study of OT receptor expression in the term-pregnant rabbit myometrium across the 24-h day is now necessary to check whether diurnal fluctuations in this underlie the diurnal pattern of uterine sensitivity to OT found here.…”

Section: Discussionmentioning

confidence: 99%

“…32, 54, 56; reviewed in Refs. 27,36) and in sensitivity of the myometrium to OT (5,34), culminating in a marked increase in the expression of OT receptors at term (1,23,48,62,67). These findings, however, have been based on the study of rather few and mainly diurnal species so that information from a wider range of animals is desirable before concluding that these observations represent a general mammalian pattern.…”

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confidence: 99%

Effect of photoperiod on the mechanical response of the pregnant rabbit uterus to oxytocin

Ninomiya-Alarcon

Hudson²,

Reyes-Guerrero³

et al. 2004

American Journal of Physiology-Regulatory, Integrative and Comp

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We present findings suggesting that photoperiod is important in determining the sensitivity of the late-pregnant rabbit uterus to oxytocin (OT). Longitudinal myometrial strips were taken from term-pregnant and estrous rabbits and mounted in an organ bath for isometric myographic recording at different times during a 16:8-h light-dark cycle (lights on 0600 -2200; n ϭ 5/group), and the strength of contractions was registered in response to the application of OT or KCl. Strength of contractions was dose dependent and was up to 200 times greater at doses three to four orders of magnitude lower in tissue taken from pregnant animals during the light phase (0700 and 1300) than during the dark phase (2400 and 0400). Strips from nonpregnant estrous females also showed greater sensitivity and contractile force when taken in the light (0700) than in the dark (0400), although the differences were not significant. Consistent with the influence of photoperiod on uterine sensitivity to OT, strips taken from two groups of pregnant females (n ϭ 5/group) maintained on a light-dark cycle advanced 12 h showed significantly greater sensitivity and force in response to OT during the new subjective light than during the new subjective dark phase. The photoperiod-dependent contractile response to OT was specific and not simply the result of a change in general mechanical properties of the muscle, because administration of KCl resulted in dose-dependent contractions of similar magnitude in both the light and dark phase. These results are consistent with the fact that rabbits, like other nocturnal mammals, typically give birth during the day. parturition; electromyographic uterine recording; circadian rhythmicity MUCH EFFORT HAS BEEN DIRECTED to understanding the processes triggering parturition, and although this is still not completely understood, some common features are emerging. One is that parturition has a strong diurnal component such that mammals usually give birth during their species-typical rest period (reviewed in Refs. 14,35,36,54): nocturnal mammals such as the rat during the day (28, 39, 52, 61) and diurnal mammals such as sheep (Ref. 30; own observations), monkeys (15,16,56), and humans (9,10,29,49,55,64) during the night. Moreover, in humans, births occurring at night are typically of shorter duration, require fewer interventions, and have an obstetrically better outcome than births occurring during the day (Refs. 3,9,55,60; reviewed in Ref. 36).A second common feature is the importance of the hormone oxytocin (OT), released at the time of parturition from the posterior pituitary into the bloodstream, in helping to initiate and sustain the uterine contractions necessary for expulsion of the fetus(es) (1, 11, 12, 17, 19, 23-25, 31, 33, 50, 67). In those species in which it has been studied, principally macaque monkeys and humans, there is a diurnal rhythm in circulating levels of OT, with the highest levels at night (18,20,33,34,36,65). This rhythm becomes more pronounced as gestation progresses and is most marked at the...

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Characterization and Expression of Oxytocin and the Oxytocin Receptor

Shojo¹,

Kaneko

2000

Molecular Genetics and Metabolism

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Changes in kinetic properties of oxytocin receptors in longitudinal muscle membranes of rat uterus during gestation

Cited by 11 publications

References 28 publications

Oxytocin‐induced phosphorylation of myosin light chain is mediated by extracellular calcium influx in pregnant rat myometrium

Oxytocin‐induced phosphorylation of myosin light chain is mediated by extracellular calcium influx in pregnant rat myometrium

Effect of photoperiod on the mechanical response of the pregnant rabbit uterus to oxytocin

Characterization and Expression of Oxytocin and the Oxytocin Receptor

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