Assessment of hemodynamic function and tolerance to ischemia in the absence or presence of calcium antagonists in hearts of Isoproterenol-treated, exercise-trained, and sedentary rats

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Abstract
The effects of cardiac hypertrophy on the structure, function andtolerance to ischemia of rat hearts have been investigated. Multipleinjections of low doses of isoproterenol (ISO) resulted in an increase ofheart weight/body weight ratio by 60%, and a decrease of myocardialcreatine kinase activity by 25%, as compared to normal rats. Compared toage-matched control rats, rats submitted to a swimming program had a higherheart weight by 20%, but similar values of heart weight to body weightratio. In isolated perfusion, the functional capacities of hearts fromISO-treated rats were severely depressed compared to normal rat heartswhereas exercise-trained rat hearts performed as well or even better thancontrol hearts. The functional recovery of ISO-treated hearts followingcardioplegia-induced arrest for 20 min at 37 degrees C was significantlyworse than the recovery of normal hearts, but hearts of exercise-trainedrats showed a significantly better recovery than control hearts. Exercisetraining results in improvement of myocardial blood supply resulting inbetter preservation of the heart during ischemia, compared to normalhearts. Addition of a combination of verapamil and diltiazem to thecardioplegic solution followed by ischemic arrest for 20 min at 37 degreesC resulted for ISO-treated rat hearts in an improved recovery of cardiacoutput (99%) compared to cardioplegia in the absence of these drugs (72%).In exercise-trained and control rat hearts, calcium antagonists improvedthe recovery from cardioplegic arrest of cardiac output from 90% to 92% andfrom 71% to 87%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

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