Potassium release from submandibular salivary gland in vitro.
Rat submandibular gland slices, incubated in continuously-gassed Krebs-Ringer bicarbonate buffer, were shown to release K+ in response to alpha-adrenergic and muscarinic cholinergic stimulation. The system employed the specific alpha-, beta-adrenergic and cholinergic receptor-blocking agents phentolamine, propranolol and atropine, respectively, in combination with the agonists L-epinephrine and carbamylcholine both of which required the presence of Ca2+ for their effect. The introduction of Ca2+ into the cell via the ionophore A23187, with all neurotransmitter receptors blocked, resulted in K+ release. Ouabain also allowed extensive K+ release which was in addition to, and hence independent of, that elicited by epinephrine and carbamylcholine. Ethacrynic acid, a potent inhibitor of salivary secretion in vivo, had no influence on K+ movement. K+ was released by both physalaemin and an eledoisin-related peptide independently of normal neurotransmitter receptors. The activity of the eledoisin-related peptide did not require the presence of extracellular Ca2+. The implication of cyclic GMP at some stage of K+ release was suggested by experiments with a phosphodiesterase inhibitor. The results support an hypothesis where the initial stimulus at either alpha-adrenergic or muscarinic cholinergic receptors causes an immediate permeability change such that Ca2+ enters the cells resulting in K+ release. The loss of K+ is quickly countered by the ouabain-sensitive (Na+ + K+) ATPase which would be activated by the lowered intracellular K+ levels.
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001692:Biological Transport; D002118:Calcium / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D004600:Eledoisin / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology; D004976:Ethacrynic Acid / Q000494:pharmacology; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D010803:Physalaemin / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism* / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D013363:Submandibular Gland / Q000187:drug effects / Q000378:metabolism*
D010656:Phenylephrine; D010803:Physalaemin; D010042:Ouabain; D004600:Eledoisin; D001285:Atropine; D002217:Carbachol; D011433:Propranolol; D007545:Isoproterenol; D004976:Ethacrynic Acid; D011188:Potassium; D002118:Calcium; D004837:Epinephrine; D010646:Phentolamine