Involvement of myosin light-chain kinase in chloride-sensitive Ca2+ influx in porcine aortic endothelial cells.
OBJECTIVE
This study was designed to investigate the involvement of myosin light-chain kinase (MLCK) in bradykinin- and thapsigargin-induced changes in intracellular Cl- and Ca2+ concentrations ([Cl-]i; [Ca2+]i) in porcine aortic endothelial cells.


METHODS
Using the fluorescent probes N-ethoxycarbonylmethyl-6-methoxyquinolinium bromide (MQAE) and fura-2/AM, the effects of different MLCK inhibitors on bradykinin- and thapsigargin-induced changes in [Cl-]i and [Ca2+]i were assessed.


RESULTS
Bradykinin and thapsigargin significantly decreased the MQAE fluorescence intensity, which indicates increased [Cl-]i; these changes were reversed by removal of extracellular chloride (Cl-o) and were significantly inhibited by Cl(-)-channel inhibitor N-phenylanthranilic acid but not by Na(+)-K(+)-Cl- cotransport inhibitor furosemide. Pretreatment with ML-9 and wortmannin, two different selective inhibitors of MLCK, significantly reduced these changes in a dose-dependent manner. The inhibitory effects of ML-9 and wortmannin on the Cl- responses were not significantly different and were not additive. Bradykinin and thapsigargin provoked large increases in [Ca2+]i, which were significantly diminished by removal of Cl-o and by pretreatment with the Cl(-)-channel inhibitor N-phenylanthranilic acid.


CONCLUSIONS
The study shows that an increase in [Cl-]i may be involved in the Ca2+ influx in response to bradykinin and thapsigargin and that MLCK might be involved in the Cl- response. We suggest that MLCK might be involved in the Cl(-)-sensitive endothelial Ca2+ responses to bradykinin and thapsigargin.
Tran
Q K
QK
Department of Internal Medicine III, Hamamatsu University School of Medicine, Japan.
Watanabe
H
H
Zhang
X X
XX
Takahashi
R
R
Ohno
R
R
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001011:Aorta; D001381:Azepines / Q000494:pharmacology; D001920:Bradykinin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000201:enzymology* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005665:Furosemide / Q000494:pharmacology; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D028021:Sodium-Potassium-Chloride Symporters; D013552:Swine; D019284:Thapsigargin / Q000494:pharmacology*; D000077191:Wortmannin; D062367:ortho-Aminobenzoates / Q000494:pharmacology
D000730:Androstadienes; D001381:Azepines; D002121:Calcium Channel Blockers; D002352:Carrier Proteins; D002712:Chlorides; D004791:Enzyme Inhibitors; D028021:Sodium-Potassium-Chloride Symporters; D062367:ortho-Aminobenzoates; C056218:ML 9; D019284:Thapsigargin; D005665:Furosemide; C001209:fenamic acid; D009219:Myosin-Light-Chain Kinase; D001920:Bradykinin; D002118:Calcium; D000077191:Wortmannin