Substance P-induced calcium entry in endothelial cells is secondary to depletion of intracellular stores.
Substance P (SP) induces an elevation in cytosolic Ca2+ concentration ([Ca2+]i) in porcine coronary artery endothelial cells by way of Ca2+ influx and release from intracellular stores. We tested the hypothesis that SP-induced Ca2+ influx occurs due to activation of a Ca(2+)-permeable influx pathway coupled to depletion of intracellular stores. With the use of the perforated patch technique and fura 2 microfluorimetry, a fivefold greater increase in [Ca2+]i per unit decrease in membrane potential was obtained in the presence of SP (10 nM) compared with resting state, implying that SP increased Ca2+ conductance. When K+ channels were blocked, SP activated a net inward current with a reversal potential (2.5 +/- 1 mV) not significantly different from that (2 +/- 1 mV) for inward current recorded in response to store depletion by (2,5-di-tert-butylhydroquinone) (BHQ, 10 microM). Increasing bath [Ca2+] induced a similar shift in reversal potential for SP- and BHQ-induced currents. Inositol 1,4,5-trisphosphate (20 microM), applied through the patch pipette, activated an inward current with Ca2+ selectivity similar to SP- and BHQ-activated currents. Dialysis of cells with heparin (5 mg/ml) completely blocked SP-induced inward current but not BHQ-induced current. These results suggest that the SP-induced increase in Ca2+ conductance can be completely explained by activation of a Ca(2+)-permeable influx pathway coupled to depletion of intracellular stores.
Sharma
N R
NR
Department of Medical Physiology, Texas A & M University Health Sciences Center, College Station 77843.
Davis
M J
MJ
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D003331:Coronary Vessels / Q000187:drug effects / Q000378:metabolism; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism*; D006493:Heparin / Q000494:pharmacology; D006873:Hydroquinones / Q000494:pharmacology; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D017136:Ion Transport / Q000187:drug effects; D008564:Membrane Potentials; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D013373:Substance P / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D013552:Swine
D006873:Hydroquinones; D026902:Potassium Channel Blockers; D015221:Potassium Channels; C019359:2,5-di-tert-butylhydroquinone; D013373:Substance P; D015544:Inositol 1,4,5-Trisphosphate; D006493:Heparin; D012964:Sodium; D000252:Calcium-Transporting ATPases; D002118:Calcium