Agonist-dependent difference in the mechanisms involved in Ca2+ sensitization of smooth muscle of porcine coronary artery.
This study was undertaken to explore possible signal-transduction mechanisms involved in the Ca2+-sensitizing effects of carbachol and endothelin-1 (ET-1) by using beta-escin-skinned smooth muscle of porcine coronary artery. Pretreatment with C3 exoenzyme of Clostridium botulinum, which selectively inactivates rho p21 by adenosine diphosphate (ADP) ribosylation, resulted in a significant inhibition of ET-1-induced Ca2+ sensitization, but had no effect on carbachol-induced Ca2+ sensitization. Whereas the protein kinase C (PKC) inhibitors calphostin C and staurosporine did not affect the Ca2+-sensitizing effect of carbachol, the tyrosine kinase inhibitors genistein and tyrphostin 25 greatly but incompletely suppressed it. In contrast, the Ca2+-sensitizing effect of ET-1 was significantly inhibited by either calphostin C or genistein. Although the inhibitory effect of calphostin C on ET-1-induced Ca2+ sensitization was less than that of genistein, the effects of calphostin C and genistein were additive. The genistein-sensitive component of ET-1-induced Ca2+ sensitization appeared to include the C3-sensitive one. However, a substantial enhancement by ET-1 of the Ca2+-induced contraction was observed even in the presence of the two inhibitors. In beta-escin-skinned smooth muscle of rabbit mesenteric artery, ET-1-induced Ca2+ sensitization was marginally affected by C3 pretreatment, calphostin C, and genistein. We conclude that, although PKC activation and rho p21 protein-dependent and -independent tyrosine phosphorylation each plays an important role in an increase in myofilament Ca2+ sensitivity, the contributions of these signaling pathways to Ca2+ sensitization are different depending on receptor agonists and tissues used. Furthermore, these data suggest the existence of an as yet undefined signal-transduction mechanism involved in Ca2+ sensitization caused by receptor agonists.
Sato
A
A
Department of Pharmacology, Hokkaido University School of Medicine, Sapporo, Japan. asato@med.hokudai.ac.jp
Hattori
Y
Y
Sasaki
M
M
Tomita
F
F
Kohya
T
T
Kitabatake
A
A
Kanno
M
M
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D002217:Carbachol / Q000494:pharmacology*; D002316:Cardiotonic Agents / Q000494:pharmacology; D003331:Coronary Vessels / Q000187:drug effects / Q000378:metabolism; D019332:Endothelin-1 / Q000494:pharmacology*; D066298:In Vitro Techniques; D008638:Mesenteric Arteries / Q000187:drug effects / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D011817:Rabbits; D013552:Swine; D014443:Tyrosine / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000378:metabolism
D002316:Cardiotonic Agents; D019332:Endothelin-1; D014443:Tyrosine; D002217:Carbachol; D011493:Protein Kinase C; D020741:rho GTP-Binding Proteins; D002118:Calcium