Increased basal contractility of cardiomyocytes overexpressing protein kinase C epsilon and blunted positive inotropic response to endothelin-1.
OBJECTIVE
Protein kinase C (PKC) is thought to be involved in the regulation of the mammalian cardiac excitation-contraction coupling process by vasoactive peptides like endothelin-1 (ET-1). However, the demonstration of a causal link between activation of specific PKC isoforms and the increase in contractility mediated by ET-1 is still inferential.


METHODS
By means of adenovirus-mediated gene transfer, we specifically overexpressed PKC epsilon in cultured adult rabbit ventricular myocytes (Ad-PKC epsilon). Myocyte shortening and [Ca2+]i transients under basal and ET-1-stimulated conditions were measured in Ad-PKC epsilon and Ad-LacZ control transfected cells.


RESULTS
Infection with Ad-PKC epsilon resulted in a strong, virus dose-dependent increase in PKC epsilon protein levels, whereas protein expression of other PKC isoforms remained unchanged. Using a multiplicity of infection of 100 plaque-forming units/myocyte, basal and cofactor-dependent PKC epsilon kinase activity was increased 28- and 90-fold, respectively, when compared to control. Myocyte basal fractional shortening and [Ca2+]i transient amplitude were both increased by 21% (P < 0.05 each) in Ad-PKC epsilon transfected myocytes when compared to Ad-LacZ transfected control myocytes. The positive inotropic effect of ET-1 in control myocytes was markedly blunted in PKC epsilon-overexpressing myocytes.


CONCLUSIONS
Specific overexpression of PKC epsilon in rabbit ventricular myocytes increases basal myocyte contractility and [Ca2+]i transients, and modifies their responsiveness to ET-1.
Baudet
S
S
Department of Cardiology and Angiology, University of Freiburg, D-79106, Freiburg, Germany. stephane.baudet@intervet.com
Weisser
J
J
Janssen
A P
AP
Beulich
K
K
Bieligk
U
U
Pieske
B
B
Noireaud
J
J
Janssen
P M
PM
Hasenfuss
G
G
Prestle
J
J
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002316:Cardiotonic Agents / Q000494:pharmacology*; D018929:Cell Culture Techniques; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000494:pharmacology*; D018014:Gene Transfer Techniques; D005822:Genetic Vectors; D006352:Heart Ventricles / Q000166:cytology / Q000201:enzymology; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology*; D009206:Myocardium / Q000201:enzymology*; D011493:Protein Kinase C / Q000378:metabolism*; D011817:Rabbits
D002316:Cardiotonic Agents; D019332:Endothelin-1; D011493:Protein Kinase C; D002118:Calcium