Capacitative calcium entry in smooth muscle cells from preglomerular vessels.
Calcium entry via voltage-gated L-type channels is responsible for at least half of the increase in cytosolic calcium ([Ca(2+)](i)) in afferent arterioles following agonist stimulation. We sought the presence of capacitative calcium entry in fresh vascular smooth muscle cells (VSMC) derived from rat preglomerular vessels. [Ca(2+)](i) was measured using fura-2 ratiometric fluorescence. Vasopressin V1 receptor agonist (V1R) (10(-7) M) increased [Ca(2+)](i) by approximately 100 nM. A calcium channel blocker (CCB), nifedipine or verapamil (10(-7) M), inhibited the response by approximately 50%. V1R in the presence of CCB increased [Ca(2+)](i) from 106 to 176 nM, confirming that calcium mobilization and/or entry may occur independent of voltage-gated channels. In nominally Ca(2+)-free buffer, V1R increased [Ca(2+)](i) from 94 to 129 nM, denoting mobilization; addition of CaCl(2) (1 mM) further elevated [Ca(2+)](i) to 176 nM, indicating a secondary phase of Ca(2+) entry. Similar responses were obtained when CCB was present in calcium-free buffer or when EGTA was present. In nominally Ca(2+)-free medium, the sarcoplasmic reticulum Ca(2+)-ATPase inhibitors (SRCAI), thapsigargin and cyclopiazonic acid (CPA), increased [Ca(2+)](i) from 97 to 128 and 143 nM, respectively, and to 214 and 220 nM, respectively, when 1 mM extracellular Ca(2+) was added. In the presence of verapamil, the results with CPA acid were nearly identical. In Ca(2+)-free buffer, the stimulatory effect of V1R or SRCAI on the Ca(2+)/fura signal was quenched by the addition of Mn(2+) (1 mM), demonstrating divalent cation entry. These studies provide evidence for capacitative (store- operated) calcium entry in VSMC freshly isolated from rat preglomerular arterioles.
Fellner
S K
SK
Department of Cell and Molecular Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7545, USA. sfellner@med.unc.edu
Arendshorst
W J
WJ
D000818:Animals; D001160:Arterioles / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D002118:Calcium / Q000378:metabolism* / Q000502:physiology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D004553:Electric Conductivity; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D007425:Intracellular Membranes / Q000378:metabolism; D007678:Kidney Glomerulus / Q000098:blood supply*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D009994:Osmolar Concentration; D051381:Rats; D011921:Rats, Inbred WKY; D017483:Receptors, Vasopressin / Q000819:agonists; D012519:Sarcoplasmic Reticulum / Q000201:enzymology; D019284:Thapsigargin / Q000494:pharmacology
D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D007211:Indoles; D017483:Receptors, Vasopressin; D019284:Thapsigargin; D000252:Calcium-Transporting ATPases; D002118:Calcium; C000543:cyclopiazonic acid