Signal transduction and Ca2+ signaling in contractile regulation induced by crosstalk between endothelin-1 and norepinephrine in dog ventricular myocardium.
In certain cardiovascular disorders, such as congestive heart failure and ischemic heart disease, several endogenous regulators, including norepinephrine (NE) and endothelin-1 (ET-1), are released from various types of cell. Because plasma levels of these regulators are elevated, it seems likely that cardiac contraction might be regulated by crosstalk among these endogenous regulators. We studied the regulation of cardiac contractile function by crosstalk between ET-1 and NE and its relationship to Ca2+ signaling in canine ventricular myocardium. ET-1 alone did not affect the contractile function. However, in the presence of NE at subthreshold concentrations (0.1 to 1 nmol/L), ET-1 had a positive inotropic effect (PIE). In the presence of NE at higher concentrations (100 to 1000 nmol/L), ET-1 had a negative inotropic effect. ET-1 had a biphasic inotropic effect in the presence of NE at an intermediate concentration (10 nmol/L). The PIE of ET-1 was associated with an increase in myofilament sensitivity to Ca2+ ions and a small increase in Ca2+ transients, which required the simultaneous activation of protein kinase A (PKA) and PKC. ET-1 elicited translocation of PKCepsilon from cytosolic to membranous fraction, which was inhibited by the PKC inhibitor GF 109203X. Whereas the Na+-H+ exchange inhibitor Hoe 642 suppressed partially the PIE of ET-1, detectable alteration of pHi did not occur during application of ET-1 and NE. The negative inotropic effect of ET-1 was associated with a pronounced decrease in Ca2+ transients, which was mediated by pertussis toxin-sensitive G proteins, activation of protein kinase G, and phosphatases. When the inhibitory pathway was suppressed, ET-1 had a PIE even in the absence of NE. Our results indicate that the myocardial contractility is regulated either positively or negatively by crosstalk between ET-1 and NE through different signaling pathways whose activation depends on the concentration of NE in the dog.
Chu
Li
L
Department of Pharmacology, Yamagata University School of Medicine, Yamagata, Japan.
Takahashi
Reiko
R
Norota
Ikuo
I
Miyamoto
Takuya
T
Takeishi
Yasuchika
Y
Ishii
Kuniaki
K
Kubota
Isao
I
Endoh
Masao
M
D000818:Animals; D020013:Calcium Signaling; D002316:Cardiotonic Agents / Q000494:pharmacology; D046508:Culture Techniques; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D019332:Endothelin-1 / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006146:Guanidines / Q000494:pharmacology; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects; D007211:Indoles / Q000494:pharmacology; D008301:Maleimides / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000502:physiology; D009638:Norepinephrine / Q000494:pharmacology*; D037342:Pertussis Toxin / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction; D013450:Sulfones / Q000494:pharmacology; D016276:Ventricular Function
D002316:Cardiotonic Agents; D019332:Endothelin-1; D004791:Enzyme Inhibitors; D006146:Guanidines; D007211:Indoles; D008301:Maleimides; D013450:Sulfones; C093373:cariporide; D037342:Pertussis Toxin; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; C070515:bisindolylmaleimide I; D009638:Norepinephrine