Role of tyrosine kinase on Ca2+ entry and refilling of agonist-sensitive Ca2+ stores in vascular smooth muscles.
Recent evidence suggests that some Ca2+ channels are regulated by a tyrosine kinase pathway. The possibility that Ca2+ entry is regulated by tyrosine kinase was investigated in canine vascular muscles. Functional studies were carried out in the dog mesenteric arteries and saphenous veins. Nicardipine-insensitive refilling of phenylephrine-sensitive Ca2+ stores of endothelium-denuded dog mesenteric artery, previously depleted of Ca2+, measured after a 30-min exposure of the arterial rings to Ca2+ in the absence and presence of genistein (10-100 microM), tyrphostin 23 (10-100 microM), tyrphostin 47 (10-100 microM), SK&F 96365 (3-30 microM), or vehicle, DMSO, as phenylephrine contraction in Ca(2+)-free medium, decreased with increasing concentrations of the inhibitors compared with DMSO-treated and control. Phenylephrine contraction in Ca(2+)-free medium was not affected in a consistent manner by tyrosine kinase inhibitors when added after the store refilling period, in Ca(2+)-free medium, 5 min prior to stimulation with phenylephrine, indicating that the inhibitors have no effect on the Ca2+ release mechanism or that they act directly on myofilaments. Cyclopiazonic acid (30 microM), an inhibitor of the sarcoplasmic reticulum Ca2+ pump, caused transient contractions in the dog saphenous vein only in the presence of extracellular Ca2+. These transient contractions were inhibited by tyrphostin 23 (30-100 microM), tyrphostin 47 (30-100 microM), genistein (30-100 microM), and SK&F 96365 (50-100 microM) but not by the vehicle DMSO. The results from this study provided evidence that a tyrosine kinase pathway is involved in the regulation of Ca2+ entry since inhibitors of tyrosine kinase are able to attenuate presumed Ca2+ entry following agonist-mediated Ca2+ store depletion. This route of Ca2+ entry is also sensitive to blockade by SK&F 96365.
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Department of Biomedical Sciences, McMaster University, Hamilton, ON, Canada.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002120:Calcium Channel Agonists / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004095:Dihydropyridines / Q000494:pharmacology; D004285:Dogs; D004730:Endothelium, Vascular / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D019833:Genistein; D007093:Imidazoles / Q000494:pharmacology; D007529:Isoflavones / Q000494:pharmacology; D008638:Mesenteric Arteries / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D010656:Phenylephrine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D004095:Dihydropyridines; D004791:Enzyme Inhibitors; D007093:Imidazoles; D007529:Isoflavones; D014662:Vasoconstrictor Agents; D010656:Phenylephrine; C038806:1,4-dihydropyridine; D019833:Genistein; D011505:Protein-Tyrosine Kinases; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D011188:Potassium; D002118:Calcium