Age-related changes in tetanic contraction of ventricular myocardium

Developmental changes of myocardial function have been described in a number of animal species. The purpose of these experiments was to assess the role of activation mechanisms in the age-related differences in twitch tension. We produced tetanic contraction of isolated ventricular trabeculae obtained from adult dogs and 4- and 25-day-old puppies. Tetanic contraction was produced using electrical stimulation at 10 Hz in modified Ringer's solution containing caffeine (10(-2)M) and calcium (10, 20, and 30 mM). This study demonstrated significant differences in the responses of adult and puppy myocardia to caffeine and calcium. The most striking finding was that active tension of puppy myocardium did not increase with tetanic contraction, whereas active tension of adult myocardium increased significantly during tetanic contraction.