ISSN:
1432-1912
Keywords:
Adrenal medulla
;
Catecholamine
;
Secretion
;
Calcium ion
;
α2-Agonists
;
α2-Adrenoceptor
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary In adrenal medullary cells, carbachol evokes the secretion of catecholamines with simultaneous uptake of45Ca. Highly selective agonists for α2-adrenoceptors, clonidine, naphazoline, guanfacine, tramazoline and oxymetazoline inhibited carbachol evoked secretion of catecholamines in a dose-dependent manner. These α2-agonists also inhibited the uptake of45Ca evoked by carbachol with similar dose-response curve to inhibition of catecholamine secretion. On the contrary, highly selective agonists for α1-adrenoceptors, phenylephrine and norfenefrine did not inhibit the secretion of catecholamines and cellular uptake of45Ca. The inhibition by α2-agonists was not restored either by the increase in carbachol, or Ca concentrations, suggesting that the mode of inhibition was distinct from competition at cholinergic receptors or Ca-channels. It is likely that α2-agonists inhibited the secretion of catecholamines via the inhibition of Ca uptake which was probably caused through the activation of α2-adrenoceptors.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00647832
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