Effects of beta-endorphin on spontaneous uterine contractions. Prostaglandins production and 45Ca2+ uptake in uterine strips from ovariectomized rats.
The effects of beta-endorphin, Met-enkephalin, dynorphin and SKF 10047 on the constancy of the isometric developed tension (IDT) of the spontaneous contractions of uterine strips isolated from ovariectomized rats were explored. beta-endorphin (10(-6) M) was the only opioid that depressed significantly uterine constancy of IDT in a concentration dependent fashion. Naloxone, neither at 10(-8) M nor at 10(-6) M, altered the negative inotropic influence of beta-endorphin. Moreover, the basal synthesis and outputs of some prostaglandins (PGE1, PGE2 and PGF2 alpha) from rat uteri and the effect of beta-endorphin (10(-6) M), were determined. It was found that the basal synthesis and release of PGs in uteri were significantly inhibited by this endogenous opioid. The effects of beta-endorphin (10(-8), 10(-6) and 10(-5) M) on the basal; and oxytocin or A23187, induced 45Ca2+ uptake, as well as the influence of naloxone were also studied. beta-endorphin at three of the concentrations tested decreased basal uterine 45Ca2+ uptake and this action was not prevented by naloxone (10(-8) M). The presence of oxytocin and of A23187 augmented significantly 45Ca2+ uptake, an effect that was antagonized by beta-endorphin (10(-6) M). The possible role of beta-endorphin in uterine functioning via the modulation of uterine PG synthesis and Ca2+ uptake is discussed.
Centro de Estudios Farmacológicos y Botánicos (CEFYBO). Consejo Nacional de Investigaciones Científicas y Técnicas, (CONICET), Buenos Aires, Argentina.
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Faletti
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Bassi
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Gimeno
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Gimeno
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004399:Dynorphins / Q000494:pharmacology; D004744:Enkephalin, Methionine / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D017136:Ion Transport / Q000187:drug effects; D010052:Ovariectomy; D010620:Phenazocine / Q000031:analogs & derivatives / Q000494:pharmacology; D011453:Prostaglandins / Q000096:biosynthesis*; D051381:Rats; D017208:Rats, Wistar; D014590:Uterine Contraction / Q000187:drug effects; D014599:Uterus / Q000187:drug effects* / Q000502:physiology; D001615:beta-Endorphin / Q000494:pharmacology*
D011453:Prostaglandins; D004744:Enkephalin, Methionine; D001615:beta-Endorphin; D004399:Dynorphins; C012134:SK&F 10047; D010620:Phenazocine; D002118:Calcium