Dawson RM, Poretski M. Assessment of a model for the opposing effects of N-ethylmaleimide on the affinity of muscarinic agonists for M2 receptors.
GENERAL PHARMACOLOGY 1992;
23:331-5. [PMID:
1511843 DOI:
10.1016/0306-3623(92)90091-w]
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Abstract
1. Homogenates of guinea pig right atrium (M2 receptors) were treated with N-ethylmaleimide, after which the ability of carbachol to inhibit binding of [3H]quinuclidinyl benzilate was studied. 2. At 37 degrees C, 10(-4) M and 10(-3) M, but not 10(-5) M, N-ethylmaleimide increased the affinity of carbachol for the receptor. At 2 degrees C, 10(-5) M and 10(-4) M, but not 10(-3) M, N-ethylmaleimide decreased carbachol affinity. At 2 degrees C, after the homogenate had been incubated at 37 degrees C without N-ethylmaleimide, 10(-5) M N-ethylmaleimide decreased carbachol affinity, as at 2 degrees C without preincubation, but 10(-3) M N-ethylmaleimide increased carbachol affinity, as at 37 degrees C. 10(-4) M N-ethylmaleimide was without effect. 3. The results are discussed with respect to a previously proposed model in which N-ethylmaleimide interacts with two sites, causing an increase or decrease in agonist affinity respectively.
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