2-Aminoethoxydiphenyl borate inhibits KCl-induced vascular smooth muscle contraction.
K(+)-depolarization (KCl)-activated Ca(2+) entry permitting sustained force-maintenance in tonic vascular smooth muscle has long been attributed solely to activation of L-type voltage-operated Ca(2+) channels (VOCs). We used the transient receptor potential channel (TRP) blocker, 2-aminoethoxydiphenyl borate (2-APB), to test the hypothesis that KCl activates additional Ca(2+) entry pathways. 2-APB alone caused a transient weak increase in force, a sustained weak increase in basal [Ca(2+)](i) and myosin light chain phosphorylation, and inhibition of KCl-induced force, [Ca(2+)](i) and myosin light chain phosphorylation. 2-APB did not appear to block VOCs, because 2-APB did not inhibit 30 nM Bay k 8644-induced increases in [Ca(2+)](i). Moreover, although 1 microM nifedipine abolished the increase in [Ca(2+)](i) produced by alpha-adrenergic receptor activation, 2-APB produced an additional reduction in [Ca(2+)](i) below the basal level. These data support the conclusion that membrane depolarization activates 2-APB-sensitive TRPs in addition to VOCs to permit strong force-maintenance in tonic vascular smooth muscle.
Ratz
Paul H
PH
Department of Biochemistry, Virginia Commonwealth University, School of Medicine, Richmond, 23298-0614, USA. phratz@vcu.edu
Berg
Krystina M
KM
D000818:Animals; D015153:Blotting, Western; D001896:Boron Compounds / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005263:Femoral Artery; D009119:Muscle Contraction / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D018994:Myosin Light Chains / Q000378:metabolism; D009543:Nifedipine / Q000494:pharmacology; D010766:Phosphorylation; D011189:Potassium Chloride / Q000494:pharmacology*; D011817:Rabbits; D012077:Renal Artery; D050051:Transient Receptor Potential Channels / Q000037:antagonists & inhibitors*
D001896:Boron Compounds; D002121:Calcium Channel Blockers; D018994:Myosin Light Chains; D050051:Transient Receptor Potential Channels; D011189:Potassium Chloride; C109986:2-aminoethoxydiphenyl borate; D009543:Nifedipine; D002118:Calcium