Suppression of myometrial contractile responses to oxytocin after different durations of chronic hypoxia in the near-term pregnant rat


      Objective: In light of our previous finding that chronic hypoxia decreases the myometrial contractile response to oxytocin in the near-term pregnant rat, we designed the current study (1) to investigate the effect of duration of hypoxic exposure on the contractile response to oxytocin and oxytocin binding sites and (2) to examine the effect of prolonged hypoxia on the contractile response to aluminum fluoride. Study design: Rats were exposed to room air (control) or to continuous hypoxia (10.5% oxygen) from day 19 through day 21 (48-hour exposure), from day 20 through day 21 (24-hour exposure), or midday 20 through day 21 of gestation (12-hour exposure). On day 21 the uterine horns were used for oxytocin receptor analysis and for in vitro study of myometrial contractile responses to cumulative doses of oxytocin (10–10 to 10–6 mol/L) or aluminum fluoride (0.5 to 4.0 mmol/L sodium fluoride in 10 μmol/L aluminum chloride). Results: The maximal contractile tensions for the control and 12-hour exposure showed no difference. In contrast, 24-hour hypoxic exposure resulted in a reduction of the maximal contractile tension from 143 ± 11 (control) to 116 ± 7 gm × sec/cm2. By 48 hours the maximal contractile tension was reduced even further, to 44 ± 13 gm × sec/cm2. Oxytocin binding sites followed a similar trend with values changing from 256.9 ± 34.9 for control to 122.9 ± 26.1 and 84.9 ± 21.3 fmol/mg protein for the 24- and 48-hour exposure groups, respectively (p < 0.01, analysis of variance), with no change in the 12-hour group. The contractile responses to aluminum fluoride were not altered. K: The suppression in the myometrial contractile response to oxytocin and oxytocin binding sites depends on the duration of hypoxic exposure. Chronic hypoxic exposure did not affect the myometrial response to aluminum fluoride.


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        • Gottfried A
        Intellectual consequences of perinatal anoxia.
        Psychol Bull. 1973; 80: 231-242
        • Longo LD
        Respiratory gas exchange in the placenta.
        in: Volume 4: handbook of physiology: the respiratory system. American Physiological Society, Washington1987: 351-401
        • Longo LD
        The biological effects of carbon monoxide on the pregnant woman and newborn infant.
        Am J Obstet Gynecol. 1977; 129: 69-103
        • Anderson RH
        • Fleming DE
        • Rhees RW
        • Kinghorn E
        Relationships between sexual activity, plasma testosterone, and the volume of the sexually dimorphic nucleus of the preoptic area in prenatally stressed and non-stressed rats.
        Brain Res. 1986; 370: 1-10
        • McCullough ML
        • Blackburn DE
        The behavioral effects of prenatal hypoxia in the rat.
        Dev Psychobiol. 1976; 9: 335-342
        • Rhee JW
        • Longo LD
        • Pearce WJ
        • Bae NH
        • Valenzuela GG
        • Ducsay CA
        Effect of chronic hypoxia on myometrial responsiveness in the pregnant rat.
        Am J Physiol. 1996; 270: E477-E482
        • Marc S
        • Lerber D
        • Harbon S
        Fluoraluminates mimic muscarinic- and oxytocin-receptor mediated generation of inositol phosphates and contraction in intact guinea pig myometrium.
        Biochem J. 1988; 225: 705-713
        • Garfield RE
        Mechanism underlying phasic contractions of pregnant rat myometrium stimulated by aluminum fluoride [letter].
        Am J Obstet Gynecol. 1995; 173: 348-349
        • Phillippe M
        Mechanisms underlying phasic contractions of pregnant rat myometrium stimulated with aluminum fluoride.
        Am J Obstet Gynecol. 1994; 170: 981-988
        • Garfield RE
        • Beir S
        Increased myometrial responsiveness to oxytocin during term and preterm labor.
        Am J Obstet Gynecol. 1989; 161: 454-461
        • Fuchs AR
        • Periyasamy S
        • Alexandrova M
        • Soloff MS
        Correlation between oxytocin receptor concentration and responsiveness to oxytocin in pregnant rat myometrium: effects of ovarian steroids.
        Endocrinology. 1983; 113: 742-749
        • Schrey MP
        • Cornford PA
        • Read AM
        • Steer PJ
        A role for phosphoinositide hydrolysis in human uterine smooth muscle during parturition.
        Am J Obstet Gynecol. 1988; 159: 964-970
        • Larcher A
        • Neculcea J
        • Breton C
        • Anslan A
        • Rozen F
        • Russo L
        • et al.
        Oxytocin receptor gene expression in the rat uterus during pregnancy and the estrous cycle and in response to gonadal steroid treatment.
        Endocrinology. 1995; 136: 5350-5356
        • Wray S
        The effect of metabolic inhibition on uterine metabolism and intracellular pH in the rat.
        J Physiol Lond. 1990; 423: 411-423
        • Wray S
        Hypoxia in the uterus.
        News Physiol Sci. 1994; 9: 88-92
        • Fuchs AR
        Plasma membrane receptors regulating myometrial contractility and their hormonal modulation.
        Semin Perinatol. 1995; 19: 15-30
        • Harvey LM
        • Gilbert RD
        • Longo LD
        • Ducsay CA
        Effects of long-term high altitude hypoxemia on adrenal responsiveness in the fetal sheep.
        Am J Physiol. 1993; 264: E741-E747
        • Beischer NA
        • Mackay EV
        in: Obstetrics and the newborn. WB Saunders, Philadelphia1986: 443-462