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

Abstract

The effects of temperature on ion fluxes and catecholamine secretion that are mediated by nicotinic acetylcholine receptors (nAChRs), voltage-sensitive calcium channels (VSCCs), and voltage-sensitive sodium channels (VSSCs) were 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 decreased more slowly at lower temperatures. The DMPP-induced responses were more sensitive to temperature changes compared to high K+-induced ones. In the measurement of intracellular sodium concentrations ([Na+](i)), it was found 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 that the secretion within the first 3 min evoked by DMPP or high K+ was greatest 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, This data suggest that temperature differentially affects the activity of nAChRs, VSCCs, and VSSCs, resulting in differential [Na+](i) and [Ca2+](i) elevation, and in the [H-3]NE secretion by adrenal chromaffin cells.