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Intracellular free Ca2+ concentration ([Ca2+]i) was monitored using the fluorescence from the dye Fura-2-AM in single myometrial cells from pregnant rats. Oxytocin and acetylcholine applied to the cell evoked an initial peak in [Ca2+]i followed by a smaller sustained rise which was rapidly terminated upon removal of acetylcholine or persisted after oxytocin(More)
Intracellular free Ca++ concentration ([Ca++]i) was monitored using the fluorescence from the dye fura-2-acetoxymethylester in single myocytes from rat portal vein. In the presence of oxodipine (a L-type Ca++ channel inhibitor), norepinephrine (10 microM) evoked transient increases in [Ca++]i which were related to release of Ca++ from intracellular stores.(More)
The presence of functional alpha 2-adrenoceptors was investigated in isolated smooth muscle cells from rat portal vein using the nystatin-perforated patch-clamp technique. The free cytoplasmic calcium concentration ([Ca2+]i) was estimated using emission from the dye Fura-2. Activation of alpha 2-adrenoceptors by clonidine (an alpha 2-adrenoceptor agonist)(More)
Previously, we have shown that myocytes from rat portal vein express alpha 1A-adrenoreceptors that couple with a Gq/G11-protein to stimulate phosphoinositide turnover and release of calcium from intracellular stores. The purpose of this study was to investigate the contribution of both alpha 1- and alpha 2-adrenoreceptor subtypes in inducing stimulation of(More)
In the pregnant rat myometrium, an averaged 30% of inositol phosphate accumulation induced by carbachol and oxytocin was inhibited by oxodipine indicating that a part of receptor-mediated generation of inositol phosphates depended on Ca++ influx through voltage-gated Ca++ channels. In fura-2-loaded cells, carbachol and oxytocin caused a two-phase [Ca++]i(More)
OBJECTIVE The purpose of our study was to characterize the membrane mechanisms responsible for oxytocin-induced depolarization in single cells from pregnant rat myometrium. STUDY DESIGN Membrane currents were recorded with the whole-cell mode of the standard patch-clamp technique. Intracellular calcium concentration was monitored with the fluorescence(More)
The effects of a novel dihydropyridine, elgodipine, and of three derivatives have been studied on the calcium channel currents of isolated cells from rat portal vein by the patch-clamp technique, and on specific (+)-[3H]isradipine binding to vascular membranes. Elgodipine inhibited both T- and L-type calcium channels in a concentration-dependent manner.(More)
We studied the effects of the enantiomers of the dihydropyridine derivative, 4-(2,3 methylenedioxyphenyl)-1,4-dihydro-2,6-dimethyl-3 carboxyethyl-5-carboxymethyl-pyridine (oxodipine), on voltage-dependent Ca2+ channels of rat portal vein myocytes by combining electrophysiological techniques and binding studies. (+)- and (-)-oxodipine depressed the L-type(More)
We studied the effects of six dihydropyridines on the specific binding of (+)-[3H]-isradipine to vascular (portal vein) and cardiac isolated membranes to achieve the relative cardiovascular selectivity of these compounds. Elgodipine, (+)-oxodipine and nifedipine had a significantly higher affinity for the vascular L-type calcium channel than for the cardiac(More)
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