Myocardial biopsy samples were taken from dogs 24 h after a period of rapid right ventricular pacing and analyzed for the presence of various isoforms of phosphodiesterase (PDE). Rapid cardiac pacing resulted in marked protection against ventricular arrhythmias (reduction in ventricular fibrillation from 60% to 10%), but no changes in PDE-specific activities were determined in these crude homogenates towards cAMP and cGMP in either the presence (stimulated activities) or the absence (basal activities) of calmodulin in both control and paced tissues. Basal cAMP hydrolytic activity was 1.7-fold more marked than the corresponding cGMP hydrolytic activity determined in the same sample. The relative proportions of PDE2, PDE3 and PDE4 in control and paced hearts were similar and for control hearts were 37.0±3%, 34.8±2.4% and 16.7±2.7%, respectively, for total cAMP hydrolytic activity. The major cGMP hydrolytic activity was PDE1 (73.8±1.4%) with the remainder ascribed to PDE2 and PDE3. It is concluded that the induction of PDE enzymes does not take place following cardiac pacing and does not account for the marked antiarrhythmic effects of this form of preconditioning.
|Number of pages||4|
|Journal||Experimental and Clinical Cardiology|
|Publication status||Published - 1997|
- phospodiesterase isozymes
- cardic pacing