Cyclic AMP formation in Tetrahymena pyriformis is controlled by a K(+)-conductance.
Responses of the cAMP generating system of Tetrahymena to changes in the concentrations of external [K+] or [Ca2+] ions were examined. When Tetrahymena are equilibrated in high [K+] buffers, intracellular levels of cAMP decreased to 40% within 2 h. Hyperpolarization of the cells by dilution of external [K+] to one-eighth of its original concentration instantly stimulated intracellular cAMP formation. Manipulations of the K+ resting conductance of Tetrahymena by equilibration in buffers of different K+ content greatly affected the responsivity of the adenylyl cyclase. Hyperpolarization of the cell by addition of Ca2+ also resulted in a rapid generation of cAMP. Blockade of K+ conductances by the K+ channel blockers tetraethylammonium, quinine, and Cs+, dose-dependently inhibited hyperpolarization-stimulated cAMP formation. The data indicate that a hyperpolarization-activated K+ current is directly coupled to adenylyl cyclase regulation.
Schultz
J E
JE
Universität Tübingen, Fakultät für Chemie und Pharmazie, Germany.
Schönborn
C
C
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002586:Cesium / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D007700:Kinetics; D011188:Potassium / Q000494:pharmacology*; D026902:Potassium Channel Blockers; D011803:Quinine / Q000494:pharmacology; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D013769:Tetrahymena pyriformis / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors
D026902:Potassium Channel Blockers; D013757:Tetraethylammonium Compounds; D002586:Cesium; D019789:Tetraethylammonium; D011803:Quinine; D000242:Cyclic AMP; D011188:Potassium; D002118:Calcium