Temperature sensitivity of catecholamine secretion and ion fluxes in bovine adrenal chromaffin cells

The effects of temperature on ion fluxes and catecholamine secretion that a re mediated by nicotinic acetylcholine receptors (nAChRs), voltage-sensitiv e calcium channels (VSCCs), and voltage-sensitive sodium channels (VSSCs) w ere investigated using bovine adrenal chromaffin cells, When the chromaffin cells were stimulated with DMPP, a nicotinic cholinergic agonist, or 50 mM K+, the intracellular calcium ([Ca2+](i)) elevation reached a peak and dec reased more slowly at lower temperatures. The DMPP-induced responses were m ore sensitive to temperature changes compared to high K+-induced ones. In t he measurement of intracellular sodium concentrations ([Na+](i)), it was fo und that nicotinic stimulation required a longer time to attain the maximal level of [Na+](i) at lower temperatures. In addition, the VSSCs-mediated [ Na+](i) increase evoked by veratridine was also reduced as the temperature decreased. The measurement of [H-3]norepinephrine (NE) secretion showed tha t the secretion within the first 3 min evoked by DMPP or high K+ was greate st at 37 degrees C. However, at 25 degrees C, the secretion evoked by DMPP, but not that by the 50 mM K+, was greater after 10 min of stimulation, Thi s data suggest that temperature differentially affects the activity of nACh Rs, VSCCs, and VSSCs, resulting in differential [Na+](i) and [Ca2+](i) elev ation, and in the [H-3]NE secretion by adrenal chromaffin cells.