[Effect of adrenergic beta-agonist on intracellular free calcium concentration in isolated acini of the parotid gland in rats].
The variations in the intracellular free calcium concentration, [Ca2+]i, have been studied in isolated acini of rat parotid gland with a fluorescent probe, fura-2. In unstimulated acini, [Ca2+]i amounted to a basal value of 180 nM. Isoproterenol used at a concentration of 200 microM, in the presence of a beta-adrenergic blocker, caused a net increase of [Ca2+]i to a mean of 90 nM above basal values. This increase was suppressed by phentolamine, an alpha-adrenergic blocker. A weak increase of [Ca2+]i of 47 nM was also obtained when acini were incubated with 1 microM isoproterenol. This effect was suppressed with 0.1 microM propranolol which, at this concentration, specifically antagonizes the beta-adrenergic receptors. We conclude that isoproterenol at 1 microM, increases the [Ca2+]i by stimulating beta-adrenergic receptors. This effect is not reproduced by forskoline. Our results suggest that this isoproterenol effect on [Ca2+]i is independent of the formation of cyclic AMP. Moreover, when the isoproterenol concentration is high (200 microM), the increase of [Ca2+]i could be through an activation of alpha-adrenergic receptors.
Sezan
A
A
Laboratoire de Biochimie des transports cellulaires (CNRS URA 1116) Bât. 432, Université Paris XI, Orsay, France.
Eboué
D
D
Rossignol
B
B
D000818:Animals; D002118:Calcium / Q000032:analysis*; D002217:Carbachol / Q000494:pharmacology; D004334:Drug Administration Schedule; D007545:Isoproterenol / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D010306:Parotid Gland / Q000737:chemistry* / Q000187:drug effects; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley
D002217:Carbachol; D011433:Propranolol; D007545:Isoproterenol; D002118:Calcium