Rapid desensitization of substance P- but not carbachol-induced increases in inositol trisphosphate and intracellular Ca++ in rat parotid acinar cells.
The effects of supramaximal concentrations of substance P and the cholinergic agonist carbachol on the accumulation of inositol trisphosphate and the elevation of the intracellular free calcium concentration were compared in rat parotid acinar cells. Substance P was fully as effective as carbachol at initial times, but there was a rapid loss of the substance P responses while the effects of carbachol were well maintained. The loss of the substance P responses represented desensitization rather than degradation of the peptide since further additions of substance P were without effect. Desensitization to substance P did not involve long-term loss of substance P receptors as it was fully reversible in less than twenty minutes, the minimum time to extensively wash previously desensitized cells.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology*; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000378:metabolism*; D007700:Kinetics; D010306:Parotid Gland / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D018040:Receptors, Neurokinin-1; D017981:Receptors, Neurotransmitter / Q000502:physiology*; D013373:Substance P / Q000494:pharmacology*; D013403:Sugar Phosphates / Q000378:metabolism*
D007295:Inositol Phosphates; D018040:Receptors, Neurokinin-1; D017981:Receptors, Neurotransmitter; D013403:Sugar Phosphates; D013373:Substance P; D015544:Inositol 1,4,5-Trisphosphate; D002217:Carbachol; D002118:Calcium