Differential regulation of high-affinity agonist binding to muscarinic sites in the rat heart, cerebellum, and cerebral cortex |
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Authors: | T W Vickroy H I Yamamura W R Roeske |
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Affiliation: | 1. Department of Pharmacology University of Arizona Health Sciences Center Tucson, Arizona 85724 USA;2. Department of Internal Medicine University of Arizona Health Sciences Center Tucson, Arizona 85724 USA;3. Department of Biochemistry University of Arizona Health Sciences Center Tucson, Arizona 85724 USA |
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Abstract: | The muscarinic agonist [3H]cismethyldioxolane ([3H]CD) was used to characterize the effects of regulators upon high-affinity agonist binding sites of the rat heart, cerebral cortex and cerebellum. Comparative studies with sodium ions (Na+), magnesium ions (Mg++), N-ethylmaleimide (NEM) and the guanine nucleotide Gpp(NH)p revealed tissue-specific effects. Mg++ preferentially enhanced while Gpp(NH)p and NEM reduced high-affinity [3H]CD binding in the heart and cerebellum. By comparison NEM enhanced high-affinity agonist binding in the cerebral cortex while Gpp(NH)p and Mg++ had little or no effect. Kinetic studies support an allosteric mechanism for these effects and provide further evidence for muscarinic receptor subtypes in mammalian tissues. |
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Keywords: | Correspondence to: William R. Roeske M.D. University of Arizona Health Sciences Center Dept. of Internal Medicine Tucson Arizona 85724 |
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