Distinct pathways of Ca(2+) sensitization in porcine coronary artery: effects of Rho-related kinase and protein kinase C inhibition on force and intracellular Ca(2+).
Alterations of the Ca(2+) sensitivity of contraction have been reported for porcine coronary artery, but the mechanisms are not clearly understood. We investigated the mechanism(s) of Ca(2+) sensitization in response to the thromboxane A(2) analogue (U46619). Our hypothesis is that different mechanisms of Ca(2+) sensitization could be distinguished by their distinct time courses. Therefore, we measured the time course of [Ca(2+)](i) and isometric force simultaneously in an intact artery after a single addition of U46619. The initial transient phase was associated with Ca(2+) release from the sarcoplasmic reticulum, whereas the maintained phase was associated with Ca(2+) influx. Two distinct types of Ca(2+) sensitization characterized these phases with either protein kinase C (PKC)-mediated or Rho-kinase-mediated mechanisms. Their effects were quite distinct on the basis of the time courses over which the sensitization was effective. PKC inhibition (1 micromol/L calphostin C) had a much greater effect in the initial phase, diminishing the size of the transient and prolonging the rise in force and the decline in [Ca(2+)](i). There were limited effects on the sustained force. Rho-kinase inhibition (10 micromol/L Y27632), in contrast, nearly abolished the sustained force but had a lesser effect on the transient phase. Neither inhibitor had any effect on the force versus [Ca(2+)](i) relations for KCl contractures. Our evidence suggests that both PKC-mediated and Rho-kinase-mediated Ca(2+) sensitizations are present in coronary arteries, but the latter is dominant in thromboxane A(2) receptor-mediated contraction.
Nobe
K
K
Department of Molecular and Cellular Physiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA.
Paul
R J
RJ
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000577:Amides / Q000494:pharmacology; D000818:Animals; D001158:Arteries / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D003331:Coronary Vessels / Q000187:drug effects / Q000378:metabolism*; D020536:Enzyme Activators / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D007537:Isometric Contraction / Q000187:drug effects; D011189:Potassium Chloride / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D011725:Pyridines / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013314:Stress, Mechanical; D013552:Swine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D054460:rho-Associated Kinases
D000577:Amides; D002121:Calcium Channel Blockers; D020536:Enzyme Activators; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D011725:Pyridines; D014662:Vasoconstrictor Agents; C108830:Y 27632; D011189:Potassium Chloride; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium