Agonist-induced changes in the modulation of K+ permeability and beating rate by muscarinic agonists in cultured heart cells
| Autor: | Jonas B. Galper, Louise C. Dziekan, Thomas W. Smith, Dennis S. Miura |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 1982 |
| Předmět: |
Agonist
medicine.medical_specialty Carbachol Physiology medicine.drug_class Scopolamine Derivatives Chick Embryo Biology Muscarinic agonist Permeability Heart Rate Internal medicine Muscarinic acetylcholine receptor medicine Animals Receptors Cholinergic Binding site Receptor Cells Cultured Binding Sites Dose-Response Relationship Drug Myocardium Muscarinic antagonist Muscarinic acetylcholine receptor M1 Articles N-Methylscopolamine Receptors Muscarinic Endocrinology Parasympathomimetics Potassium medicine.drug |
| Zdroj: | The Journal of General Physiology |
| ISSN: | 1540-7748 0022-1295 |
| Popis: | The correlation between number of muscarinic cholinergic receptor sites as measured by binding of the muscarinic antagonist [3H]methylscopolamine ([3H]MS) and the ability of muscarinic agonists to mediate a physiologic response was determined in intact heart cells cultured from chick embryos 10 d in ovo. The increase in K+ permeability and the decrease in beating rate mediated by the muscarinic agonist carbamylcholine were the responses studied. Exposure to 10(-3) M carbamylcholine caused a 15% decrease in beating rate and a 33% increase in the rate of 42K+ efflux from cells labeled to equilibrium. An assay for binding of [3H]MS to intact cells was developed. [3H]MS bound specifically to intact heart cells (185 fmol/mg protein) with a Kd of 0.48 nM. Exposure of cells for various times to 10(-3) M carbamylcholine followed by binding of [3H]MS to intact cells demonstrated that a gradual loss of 70% of [3H]MS binding sites took place over the next 6 h with a T 1/2 of 30 min. A decrease in the ability of carbamylcholine to stimulate K+ efflux and to decrease beating rate was observed after pre-exposure of cells to muscarinic agonists. A close correlation was found between the loss of the subclass of muscarinic receptors subject to agonist control and the loss of physiologic responsiveness after agonist exposure. The data suggest the absence of significant numbers of "spare" receptors within this group. |
| Databáze: | OpenAIRE |
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