Muscarinic receptor-stimulated Ca2+ signaling and inositol lipid metabolism in avian salt gland cells.
Activation of muscarinic cholinergic receptors was studied by measuring agonist-stimulated inositol lipid turnover and changes in [Ca2+]i in dissociated salt gland secretory cells. Carbachol stimulation of quin2-loaded cells results in a sustained 4-fold increase in [Ca2+]i, while incorporation of [32P]Pi into phosphatidylinositol (PI) and phosphatidate are similarly increased. [3H]Inositol phosphates, measured in the presence of Li+, increased 13-fold. The stimulated increment in [Ca2+]i required extracellular Ca2+, whereas [3H]inositol phosphate accumulation was independent of external Ca2+. Dose-response curves for carbachol-induced increments in [Ca2+]i, PI labeling, and labeled inositol phosphate release are similar, with EC50 values of 6, 4.5 and 8 microM, respectively. Dissociation constants for atropine vs. the quin2 and phospholipid responses are 0.59 +/- 0.3 nM and 0.48 +/- 0.28 nM, respectively. These cells thus provide a model system for the study of non-exocytotic secretion as a consequence of stimulated inositol lipid turnover.
D000634:Aminoquinolines; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004372:Ducks; D007295:Inositol Phosphates / Q000378:metabolism*; D010890:Pirenzepine / Q000494:pharmacology; D011950:Receptors, Cholinergic / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000378:metabolism*; D012491:Salt Gland / Q000378:metabolism*; D013403:Sugar Phosphates / Q000378:metabolism*
D000634:Aminoquinolines; D007295:Inositol Phosphates; D011950:Receptors, Cholinergic; D011976:Receptors, Muscarinic; D013403:Sugar Phosphates; D010890:Pirenzepine; D002217:Carbachol; C035739:Quin2; D002118:Calcium