Activation of alpha-1A adrenoceptors mobilizes calcium from the intracellular stores in myocytes from rat portal vein.

International audience; 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. The alpha-1 adrenoceptors mediating intracellular Ca++ release and inositol phosphate accumulation were identified by using subtype-selective agonists and antagonists. Pretreatment with chloroethylclonidine had little effect on the norepinephrine-induced increase in [Ca++]i and inositol phosphate accumulation. In c…