Coupling of muscarinic receptors to the mobilization of intracellular Ca2+ stores in permeabilized SH-SY5Y human neuroblastoma cells.
Intracellular stores of Ca2+ were mobilized transiently by carbachol in suspensions of electrically permeabilized SH-SY5Y cells. The kinetics and the dose-dependence of this mobilization paralleled carbachol-induced increases in inositol 1,4,5-trisphosphate (InsP3) mass [for both parameters EC50 (concn. giving half-maximal response) = 60-70 microM]. Guanosine 5'-[gamma-thio]triphosphate enhanced the maximal effect and the potency of carbachol on Ca2+ mobilization and InsP3 mass, but caused separation of the dose-response curves (EC50 = 0.6 microM and 5.6 microM respectively). These data show that functional coupling of muscarinic receptors to Ca2+ mobilization can be maintained after permeabilization, reveal major effects of guanine nucleotides on agonist-induced Ca2+ mobilization and provide a basis for explanation of discrepancies between agonist potency on InsP3 concentration and Ca2+ mobilization in intact cells.
Wojcikiewicz
R J
RJ
Department of Pharmacology and Therapeutics, University of Leicester, U.K.
Safrany
S T
ST
Challiss
R A
RA
Strupish
J
J
Nahorski
S R
SR
D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D002217:Carbachol / Q000494:pharmacology; D002460:Cell Line; D002463:Cell Membrane Permeability; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D007295:Inositol Phosphates / Q000378:metabolism; D007700:Kinetics; D009447:Neuroblastoma; D011976:Receptors, Muscarinic / Q000378:metabolism*
D002132:Calcium Radioisotopes; D007295:Inositol Phosphates; D011976:Receptors, Muscarinic; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D002217:Carbachol; D002118:Calcium