Kinetic effects of terbium ions on muscarinic acetylcholine receptors of murine neuroblastoma cells.
Preincubation of murine neuroblastoma cells (clone N1E-115) with terbium chloride resulted in a significant potentiation of carbachol-mediated increase in cyclic GMP formation. This effect was accompanied by a shift of the peak response from 30 s to 120 s and a 6-fold decrease in carbachol concentration producing half-maximal responses, in addition to a significant increase in the Hill coefficient. Terbium ions also caused a significant decrease in the affinity and an increase in the maximum binding of [3H]quinuclidinyl benzilate to muscarinic receptors, the change in affinity being mainly due to a decrease in the association rate. Preincubation of cells with 1 mM carbachol for 4 h (the desensitized state of the muscarinic receptor) resulted in a decrease in the ability of terbium to alter [3H]quinuclidinyl benzilate binding. The effects of terbium reported here might be due to its affecting muscarinic receptor-effector coupling, which is considered to be lost upon receptor desensitization.
D000818:Animals; D002460:Cell Line; D006152:Cyclic GMP / Q000378:metabolism; D007700:Kinetics; D051379:Mice; D009447:Neuroblastoma / Q000378:metabolism*; D011813:Quinuclidinyl Benzilate / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000378:metabolism*; D013725:Terbium / Q000494:pharmacology*
D011976:Receptors, Muscarinic; D013725:Terbium; D011813:Quinuclidinyl Benzilate; D006152:Cyclic GMP