Increased protein synthesis is necessary for the development of late preconditioning against myocardial stunning.
In phase I of this study, the rate of protein synthesis was measured by the incorporation of [(3)H]leucine into the protein pool in the heart of conscious rabbits. At 2 h after ischemic preconditioning (PC) with six 4-min occlusion/4-min reperfusion (O/R) cycles (group II), the [3H]leucine content in the ischemic-reperfused region was increased by 82% compared with that in controls (group I), indicating increased protein synthesis. This increase was completely abrogated by pretreatment with cycloheximide (CH; group III). In phase II, rabbits underwent six O/R cycles for three consecutive days (days 1-3). Controls (group IV) exhibited late PC against myocardial stunning on days 2 and 3. In group V, which received CH 30 min before the 1st O/R cycle on day 1 (same dose as group III), late PC against stunning on day 2 was completely abrogated. In group VI, pretreatment with CH 24 h before the 1st sequence of O/R cycles had no effect on myocardial stunning on day 1, indicating that the absence of late PC on day 2 in group V cannot be ascribed to delayed toxicity of CH. Taken together, these results demonstrate that, in the conscious rabbit, ischemic PC causes a rapid increase in myocardial protein synthesis and that this increased protein synthesis (or at least a fraction of it) is necessary for the development of the protection against myocardial stunning 24 h later. The late phase of ischemic PC is therefore dependent on the formation of new proteins in intact animals.
Rizvi
A
A
Experimental Research Laboratory, Division of Cardiology, University of Louisville and Jewish Hospital Heart and Lung Institute, Louisville, Kentucky 40292, USA.
Tang
X L
XL
Qiu
Y
Y
Xuan
Y T
YT
Takano
H
H
Jadoon
A K
AK
Bolli
R
R
D000818:Animals; D003513:Cycloheximide / Q000494:pharmacology; D019157:Ischemic Preconditioning, Myocardial; D007930:Leucine; D008297:Male; D009124:Muscle Proteins / Q000096:biosynthesis*; D017682:Myocardial Stunning / Q000378:metabolism* / Q000503:physiopathology* / Q000517:prevention & control; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011817:Rabbits; D014316:Tritium
D009124:Muscle Proteins; D011500:Protein Synthesis Inhibitors; D014316:Tritium; D003513:Cycloheximide; D007930:Leucine