Catecholamines-evoked cytosolic ca2+rise in endothelial cells from bovine adrenal medulla

The effects of catecholamines on intracellular Ca²⁺concentrations ([Ca²⁺]_i) in single acutely dissociated bovine adrenal medulla endothelial cells (BAMECs) were measured using the intracellular fluorescent probe Fluo-3 AM. 100 m epinephrine or norepinephrine induced a biphasic [Ca²⁺]_i rise with an initial peak followed by a delayed phase. 10 m phenylephrine (₁-adrenergic agonist) caused a [Ca²⁺]_i rise similar to that evoked by catecholamines. The increase in [Ca²⁺]_i induced by 10 m phenylephrine was reverted by 10 m phenoxybenzamine (-adrenergic antagonist). Neither isoproterenol (-adrenergic agonist) nor clonidine (₂-adrenergic agonist) induced [Ca²⁺]_i rise. The initial peak was insensitive to zero external Ca²⁺ and it was abolished after Ca²⁺ internal storages were emptied by 10 mM caffeine. The delayed phase was reduced to near zero by external Ca²⁺ removal. These results indicate that BAMECs possess ₁-adrenergic receptors associated to both the release of caffeine-sensitive intracellular Ca²⁺ stores and the entry of extracellular Ca²⁺ We suggest that chromaffin cell secretion may activate BAMECs in vivo through an increase in [Ca²⁺]_i which could induce the secretion of vasoactive factors allowing a rapid entry of hormones into the circulation. (Mol Cell Biochem 000: 000-000,1999)