Journal of the Society for Gynecologic Investigation · 1996
The mechanisms underlying Bay K 8644-stimulated phasic myometrial contractions.
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Chien E K, Saunders T, Phillippe M
Аннотация
OBJECTIVE: Phasic myometrial contractions appear to be produced by calcium transients resulting from the activation of the phosphatidylinositol-signaling pathway. Bay K 8644, an L-type calcium channel activator, produces an increase in frequency and intensity of phasic myometrial contractions. These studies were performed to test the hypothesis that Bay K 8644-stimulated contractions were mediated through mechanisms involving phosphoinositide-specific phospholipase C activation and cytosolic calcium oscillation-like mechanisms.
METHODS: In vitro contraction studies and intracellular calcium imaging were performed on longitudinal strips of uterine tissue obtained from mature virgin Sprague-Dawley rats. Isometric contraction data were computer digitized, analyzed for contraction area, and normalized for cross-sectional area. Dose-response studies were performed using previously reported inhibitors of cytosolic calcium oscillation mechanisms. In addition, qualitative inositol-phosphate production studies were performed after prelabeling uterine tissue in vitro with 3H-inositol. Subsequently, the labeled inositol phosphates were separated and recovered using anion exchange chromatography.
RESULTS: Bay K 8644 produced periodic calcium transients or oscillations along with a dose-related increase in contractile activity and a significant increase in inositol-phosphate production. In contrast, neomycin (an inhibitor of phospholipase C), adenine (an inhibitor of calcium-induced calcium release), nifedipine (an L-type calcium channel blocker), and EGTA (a calcium chelator) significantly inhibited Bay K 8644-stimulated contractile activity.
CONCLUSIONS: These results are consistent with the hypothesis that Bay K 8644, through its facilitation of increased intracellular calcium, results in the activation of the phosphatidylinsitol-signaling pathway and cytosolic calcium oscillation-like phenomena, thereby resulting in the generation of phasic myometrial contractions.
METHODS: In vitro contraction studies and intracellular calcium imaging were performed on longitudinal strips of uterine tissue obtained from mature virgin Sprague-Dawley rats. Isometric contraction data were computer digitized, analyzed for contraction area, and normalized for cross-sectional area. Dose-response studies were performed using previously reported inhibitors of cytosolic calcium oscillation mechanisms. In addition, qualitative inositol-phosphate production studies were performed after prelabeling uterine tissue in vitro with 3H-inositol. Subsequently, the labeled inositol phosphates were separated and recovered using anion exchange chromatography.
RESULTS: Bay K 8644 produced periodic calcium transients or oscillations along with a dose-related increase in contractile activity and a significant increase in inositol-phosphate production. In contrast, neomycin (an inhibitor of phospholipase C), adenine (an inhibitor of calcium-induced calcium release), nifedipine (an L-type calcium channel blocker), and EGTA (a calcium chelator) significantly inhibited Bay K 8644-stimulated contractile activity.
CONCLUSIONS: These results are consistent with the hypothesis that Bay K 8644, through its facilitation of increased intracellular calcium, results in the activation of the phosphatidylinsitol-signaling pathway and cytosolic calcium oscillation-like phenomena, thereby resulting in the generation of phasic myometrial contractions.
Предметные рубрики MeSH
3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl esterAdenineAnalysis of VarianceAnimalsCalciumCalcium ChannelsCalcium Channels, L-TypeEgtazic AcidEstrusFemaleIn Vitro TechniquesInositol PhosphatesIsometric ContractionModels, BiologicalMyometriumNifedipineOxytocinProestrusRatsRats, Sprague-DawleySignal TransductionUterine Contraction