The role of calcium in the receptor mediated control of potassium permeability in the rat lacrimal gland.
1. In the presence of extracellular Ca, adrenaline stimulated a large increase in the rate of K (86Rb) release from rat lacrimal slices, followed by a lower, more sustained rate. 2. In the absence of extracellular Ca, adrenaline elicited only a transient release of 86Rb. 3. The artificial introduction of Ca into the cytosol by the ionophore A-23187 could also initiate the release of 86Rb. 4. In a zero-Ca medium, if either adrenaline or carbachol produced a transient release of 86Rb, the tissue could not respond to the other agonist with a transient release unless Ca was momentarily reintroduced to the medium. 5. If Ca was present in a limiting concentration, the Ca-dependent rate of 86Rb release elicited from a lacrimal slice exposed simultaneously to carbachol and adrenaline was not significantly different from the release seen with carbachol alone. 6. It is concluded that the agonist-induced release of K from the lacrimal gland consists of both a Ca-independent phase which is initiated by the release of a limited pool of Ca, and a Ca-dependent phase which is mediated by the influx of extracellular Ca. 7. It is also concluded that both alpha-adrenergic and muscarinic receptor occupation activate a common, post-receptor mechanism which may be responsible for both phases of K release.
D000818:Animals; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D002217:Carbachol / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects; D004837:Epinephrine / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D007765:Lacrimal Apparatus / Q000378:metabolism*; D008297:Male; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D011941:Receptors, Adrenergic / Q000502:physiology*; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D011950:Receptors, Cholinergic / Q000502:physiology*; D011976:Receptors, Muscarinic / Q000502:physiology*
D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D011950:Receptors, Cholinergic; D011976:Receptors, Muscarinic; D002217:Carbachol; D011188:Potassium; D002118:Calcium; D004837:Epinephrine