Propofol decreases myofilament Ca2+ sensitivity via a protein kinase C-, nitric oxide synthase-dependent pathway in diabetic cardiomyocytes.
BACKGROUND
The authors' objective was to assess the role of protein kinase C (PKC) and nitric oxide synthase (NOS) in mediating the effects of propofol on diabetic cardiomyocyte contractility, intracellular free Ca2+ concentration ([Ca2+]i), and myofilament Ca2+ sensitivity.


METHODS
Freshly isolated ventricular myocytes were obtained from normal and diabetic rat hearts. [Ca2+]i and cell shortening were simultaneously measured in electrically stimulated, ventricular myocytes using fura-2 and video-edge detection, respectively. Actomyosin adenosine triphosphatase activity and troponin I (TnI) phosphorylation were assessed in [32P]orthophosphate-labeled myofibrils. Western blot analysis was used to assess expression of PKC and NOS.


RESULTS
Propofol (10 microM) decreased peak shortening by 47 +/- 6% with little effect on peak [Ca2+]i (92 +/- 5% of control) in diabetic myocytes. Maximal actomyosin adenosine triphosphatase activity was reduced by 43 +/- 7% and TnI phosphorylation was greater (32 +/- 6%) in diabetic myofibrils compared with normal. Propofol reduced actomyosin adenosine triphosphatase activity by 17 +/- 7% and increased TnI phosphorylation in diabetic myofibrils. PKC inhibition prevented the propofol-induced increase in TnI phosphorylation and decrease in shortening. Expression of PKC-alpha, PKC-delta, PKC-epsilon, and constitutive NOS were up-regulated and inducible NOS was expressed in diabetic cardiomyocytes. NOS inhibition attenuated the propofol-induced decrease in shortening.


CONCLUSIONS
Myofilament Ca2+ sensitivity and, to a lesser extent, peak [Ca2+]i are decreased in diabetic cardiomyocytes. Increases in PKC and NOS expression in combination with TnI phosphorylation seem to contribute to the decrease in [Ca2+]i and myofilament Ca2+ sensitivity. Propofol decreases [Ca2+]i and shortening via a PKC-, NOS-dependent pathway.
Wickley
Peter J
PJ
Kent State University, Kent, Ohio, USA.
Shiga
Toshiya
T
Murray
Paul A
PA
Damron
Derek S
DS
D008841:Actin Cytoskeleton / Q000187:drug effects*; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects*; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000378:metabolism; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000378:metabolism; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000187:drug effects*; D009210:Myofibrils / Q000187:drug effects / Q000201:enzymology; D009218:Myosins / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000502:physiology*; D010710:Phosphates / Q000378:metabolism; D015742:Propofol / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects*; D019210:Troponin I / Q000378:metabolism
D018686:Anesthetics, Intravenous; D001786:Blood Glucose; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D010710:Phosphates; D019210:Troponin I; D019001:Nitric Oxide Synthase; D011493:Protein Kinase C; D009218:Myosins; D015742:Propofol