ATP-mediated Ca2+ signaling in preglomerular smooth muscle cells.

Academic Article

Abstract

  • We performed studies to determine the effect of extracellular ATP on the intracellular Ca2+ concentration ([Ca2+]i) in freshly isolated microvascular smooth muscle cells (MVSMC). Suspensions of preglomerular MVSMC were prepared by enzymatic digestion and loaded with fura 2. Single cells were studied using a microscope-based fluorescence spectrophotometer during superfusion of a physiological salt solution with 1.8 mM Ca2+ and during exposure to similar solutions containing ATP. Under control conditions, baseline [Ca2+]i averaged 107 +/- 6 nM (n = 86 cells from 34 animals). ATP administration elicited concentration-dependent increases in [Ca2+]i. Exposure to ATP concentrations of 1, 10, and 100 microM increased intracellular Ca2+ to peak concentrations of 133 +/- 20, 338 +/- 37, and 367 +/- 35 nM, respectively (P < 0.05 vs. respective baseline). Steady-state [Ca2+]i increased to 113 +/- 15, 150 +/- 16 (P < 0.05 vs. baseline), and 180 +/- 12 nM (P < 0.05 vs. baseline) for the same groups. The [Ca2+]i response to ATP was also assessed in the absence of extracellular Ca2+ and during blockade of L-type Ca2+ channels with diltiazem. In these studies, exposure to 100 microM ATP induced a transient peak increase in [Ca2+]i with the plateau phase being totally abolished under Ca2+-free conditions and markedly attenuated during Ca2+ channel blockade, respectively. These data indicate that ATP-mediated P2-receptor activation increases [Ca2+]i in freshly isolated preglomerular MVSMC by stimulating Ca2+ release from intracellular stores, in addition to stimulating the influx of extracellular Ca2+ through voltage-gated L-type Ca2+ channels.
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    Keywords

  • Adenosine Triphosphate, Animals, Arteries, Arterioles, Calcium, Calcium Channel Blockers, Calcium Channels, Calcium Channels, L-Type, Calcium Signaling, Diltiazem, Dose-Response Relationship, Drug, Homeostasis, In Vitro Techniques, Intracellular Membranes, Kidney Glomerulus, Male, Muscle, Smooth, Vascular, Osmolar Concentration, Rats, Rats, Sprague-Dawley
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    Author List

  • Inscho EW; Schroeder AC; Deichmann PC; Imig JD
  • Start Page

  • F450
  • End Page

  • F456
  • Volume

  • 276
  • Issue

  • 3