Alpha- and beta-adrenergic stimulation of parenchymal cell Ca2+ influx. Influence of extracellular pH.
Stimulation of parenchymal cell alpha- and beta-adrenergic receptors, with either epinephrine or the specific alpha-agonist phenylephrine or the beta-agonist isoproterenolol, promoted a net Ca2+ influx when the pH of the external medium was greater than pH 7.7. The effect was both time- and dose-dependent. At the elevated pH of 8.1, alpha-adrenergic receptors were still able to mobilize intracellular Ca2+, since when the external Ca2+ concentration was reduced to 0.05 mM, epinephrine promoted net Ca2+ efflux. The data suggest the existence of a Ca2+/H+ antiport or a Ca2+/OH- symport in the plasma membrane which can be stimulated by either alpha- or beta-adrenergic receptors. It is proposed that the Ca2+ influx mediated by alpha-adrenergic receptors helps maintain the elevated cytosolic [Ca2+]i for longer time periods after the initial mobilization from intracellular Ca2+ stores.
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004837:Epinephrine / Q000494:pharmacology*; D005934:Glucagon / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D006005:Phosphorylases / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D014667:Vasopressins / Q000494:pharmacology
D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D014667:Vasopressins; D000804:Angiotensin II; D005934:Glucagon; D006005:Phosphorylases; D002118:Calcium; D004837:Epinephrine