Temperature Dependence of Catecholamine Secretion from Cultured Bovine Chromaffin Cells |
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Authors: | Lung-Sen Kao Edward W. Westhead |
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Affiliation: | Department of Biochemistry, University of Massachusetts, Amherst, Massachusetts, U.S.A. |
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Abstract: | Abstract: Secretion of both epinephrine and norepinephrine by cultured chromaffin cells was studied at temperatures ranging from 0°C to 37°C. The percentage of epinephrine secreted was always lower than that of norepinephrine when the cells were stimulated with either acetylcholine or high K+ at any temperature. When the cells were stimulated with acetylcholine or carbachol the percentage of catecholamine secreted at 10 min increased with temperature from 4°C to 24°C and then decreased from 24°C to 37°C. Potassium-stimulated cells secreted increasing amounts of catecholamine as the temperature was increased to 37°C. We found, however, that the initial rates of secretion increased continuously as temperature increased throughout the range for both carbachol-and K+-stimulated cells. The temperature maximum of acetylcholine-stimulated secretion is caused by a faster shut-off of secretion at higher temperature. The Arrhenius plots of initial rates show an inflection point at approximately 17°C for carbachol-stimulated cells. The plot for K+-stimulated cells is a straight line over the entire temperature range. The transition could be caused by a conformational change in the cholinergic receptor/ion channel molecule. |
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Keywords: | Bovine chromaffin cells Secretion Temperature dependence |
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