Effects of endothelin-1 on Ca2+ signaling in guinea-pig ventricular myocytes: role of protein kinase C.
The effects of ET-1 on contraction, Ca2+ transient and L-type Ca2+ current (ICa.L) were studied in single cells isolated from ventricles of guinea-pig hearts. The aim of our study was to elucidate the mechanism of the positive inotropic effect during endothelin receptor stimulation by focusing on the role of PKC. ET-1 at concentrations of 5 and 10 nM produced a biphasic pattern of inotropism: a first decrease in contraction by 34.4 +/- 2.5% of the control followed by a sustained increase in contraction by 66.6 +/- 8.4% (mean +/- SEM, n = 9). The Ca2+ transient decreased by 13.5 +/- 1.0% during the negative inotropic phase, while it increased by 58.1 +/- 8.4% (n = 10) during the positive inotropic phase. Using the whole-cell voltage-clamp technique with conventional microelectrodes, the application of ET-1 (5 nM) increased the ICa.L by 32.6 +/- 5.1% (n = 10), which was preceded by a short-lived decrease in ICa.L. Incubation of myocytes with pertussis toxin (PTX, at 2 micrograms/ml for > 3 h at 35 degrees C) failed to block the ET-1-induced enhancement of ICa.L. The increases in contraction, Ca2+ transient, and ICa.L by ET-1 were inhibited by pretreatment with 5-N-methyl-N-isobutyl amiloride (MIA; 10 microM), an amiloride analog, and a novel selective Na+/H+ exchange inhibitor HOE694 (10 microM). To determine whether activation of protein kinase C (PKC) is responsible for the enhancement of ICa.L by ET-1, we tested a PKC inhibitor, GF109203X, and found that it does exert an inhibitory effect on the ET-1-induced ICa.L increase. Our study suggests that during ET receptor stimulation an increase in ICa.L due to stimulation of Na+/H+ exchange via PKC activation causes an increase in Ca2+ transients and thereby in the contractile force of the ventricular myocytes.
Woo
S H
SH
Department of Life Sciences, Pohang University of Science and Technology, Kyungbuk, Republic of Korea.
Lee
C O
CO
D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002316:Cardiotonic Agents / Q000494:pharmacology; D002478:Cells, Cultured; D004594:Electrophysiology; D019332:Endothelin-1 / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006146:Guanidines / Q000494:pharmacology; D006168:Guinea Pigs; D007211:Indoles / Q000494:pharmacology; D008297:Male; D008301:Maleimides / Q000494:pharmacology; D009200:Myocardial Contraction / Q000502:physiology; D009206:Myocardium / Q000378:metabolism*; D010477:Perfusion; D037342:Pertussis Toxin; D011493:Protein Kinase C / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D013450:Sulfones / Q000494:pharmacology; D013997:Time Factors; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D002316:Cardiotonic Agents; D019332:Endothelin-1; D004791:Enzyme Inhibitors; D006146:Guanidines; D007211:Indoles; D008301:Maleimides; D013450:Sulfones; D010566:Virulence Factors, Bordetella; C074107:3-methylsulfonyl-4-piperidinobenzoyl guanidine; D000584:Amiloride; C056369:5-(N-methyl-N-isobutyl)amiloride; D037342:Pertussis Toxin; D011493:Protein Kinase C; C070515:bisindolylmaleimide I; D002118:Calcium