Role of PKC, tyrosine kinases, and Rho kinase in -adrenoreceptor-mediated PASM contraction

Damron, Derek S., Noriaki Kanaya, Yasuyuki Homma, Si-Oh Kim, and Paul A. Murray. Role of PKC, tyrosine kinases, and Rho kinase in -adrenoreceptor-mediated PASM contraction. Am J Physiol Lung Cell Mol Physiol 283: L1051–L1064, 2002. First published July 12, 2002; 10.1152/ajplung.00345.2001.—Our objectives were to identify the relative contributions of intracellular free Ca2 concentration ([Ca2 ]i) and myofilament Ca2 sensitivity in the pulmonary artery smooth muscle (PASM) contractile response to the -adrenoreceptor agonist phenylephrine (PE) and to assess the role of PKC, tyrosine kinases (TK), and Rho kinase (ROK) in that response. Our hypothesis was that multiple signaling pathways are involved in the regulation of [Ca2 ]i, myofilament Ca2 sensitization, and vasomotor tone in response to -adrenoreceptor stimulation of PASM. Simultaneous measurement of [Ca2 ]i and isometric tension was performed in isolated canine pulmonary arterial strips loaded with fura 2-AM. PE-induced tension development was due to sarcolemmal Ca2 influx, Ca2 release from inositol 1,4,5-trisphosphate-dependent sarcoplasmic reticulum Ca2 stores, and myofilament Ca2 sensitization. Inhibition of either PKC or TK partially attenuated the sarcolemmal Ca2 influx component and the myofilament Ca2 sensitizing effect of PE. Combined inhibition of PKC and TK did not have an additive attenuating effect on PE-induced Ca2 sensitization. ROK inhibition slightly decreased [Ca2 ]i but completely inhibited myofilament Ca2 sensitization. These results indicate that PKC and TK activation positively regulate sarcolemmal Ca2 influx in response to -adrenoreceptor stimulation in PASM but have relatively minor effects on myofilament Ca2 sensitivity. ROK is the predominant pathway mediating PE-induced myofilament Ca2 sensitization.