Calcium signaling pathways utilized by P2X receptors in freshly isolated preglomerular MVSMC

This study tested the hypothesis that P2X receptor activation increases intracellular Ca2+concentration ([Ca2+]i) in preglomerular microvascular smooth muscle cells (MVSMC) by evoking voltage-dependent calcium influx. MVSMC were obtained and loaded with the calcium-sensitive dye fura 2 and studied by using single-cell fluorescence microscopy. The effect of P2X receptor activation on [Ca2+]i was assessed by using the P2X receptor-selective agonist α,β-methylene-ATP and was compared with responses elicited by the endogenous P2 receptor agonist ATP. α,β-Methylene-ATP increased [Ca2+]i dose dependently. Peak increases in [Ca2+]iaveraged 37 ± 11, 73 ± 15, and 103 ± 21 nM at agonist concentrations of 0.1, 1, and 10 μM, respectively. The average peak response elicited by 10 μM α,β-methylene-ATP was ∼34% of the response obtained with 10 μM ATP. α,β-Methylene-ATP induced a transient increase in [Ca2+]i before [Ca2+]i returned to baseline, whereas ATP induced a biphasic response including a peak response followed b...