Guanine nucleotides regulate [3H]substance P binding in rat small intestine.
The binding of [3H]substance P (SP) to membranes of the rat small intestine demonstrates specific binding to receptors having more than one affinity for SP. The values of the binding parameters for the high-affinity site obtained from a non-linear regression analysis are as follows: KD = 0.25 nM, Bmax = 149.5 fmol/mg protein. Inhibition curves of 3H-SP binding using various unlabeled tachykinins show that the high-affinity receptor is of the P-subtype, having the highest affinity for SP and lower affinities for eledoisin and kassinin. Guanine nucleotides and sodium independently reduce the binding of 3H-SP to the high-affinity receptor in a dose-related manner; GTP and GDP are more potent than GMP. The reduction of specific SP binding by GTP can be ascribed primarily to an increase in the off-rate. The effects of guanine nucleotides on 3H-SP binding to membranes of rat small intestine suggest that the high-affinity receptor is linked to an effector by a GTP-binding regulatory protein.
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D000818:Animals; D001667:Binding, Competitive; D002462:Cell Membrane / Q000378:metabolism; D006150:Guanine Nucleotides / Q000494:pharmacology*; D007421:Intestine, Small / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D018040:Receptors, Neurokinin-1; D017981:Receptors, Neurotransmitter / Q000187:drug effects / Q000378:metabolism*; D013373:Substance P / Q000378:metabolism*
D006150:Guanine Nucleotides; D018040:Receptors, Neurokinin-1; D017981:Receptors, Neurotransmitter; D013373:Substance P