AJP - Heart and Circulatory Physiology, Vol 259, Issue 6 1637-H1642, Copyright © 1990 by American Physiological Society

ARTICLES

Ontogeny of adenosine response in guinea pig heart and aorta

G. P. Matherne, J. P. Headrick and R. M. Berne
Department of Physiology, University of Virginia, Charlottesville 22908.

Effects of maturation on the responses of isolated perfused hearts and aortic rings to adenosine were examined. Dose-response relationships for adenosine were obtained in aortic rings and hearts isolated from immature (5 days) and mature (1-2 mo) guinea pigs. Immature and mature hearts were perfused at constant flows of 9.9 +/- 0.3 and 9.5 +/- 0.4 ml.min-1.g-1, respectively, and displayed basal resistances of 4.8 +/- 0.1 and 6.7 +/- 0.2 mmHg.ml-1.min.g. Immature hearts were more sensitive to exogenous adenosine, displaying a significantly lower 50% effective concentration (EC50, 2.5 x 10(-8) M) than mature hearts (1.1 x 10(-7) M, P less than 0.05). Adenosine induced dilation at a lower threshold dose in immature hearts (3 x 10(-9) M, 6.0 +/- 0.3% relaxation) than in mature hearts (10(-8) M, 3.1 +/- 1.3% relaxation). The time required to elicit 50% of the observed dilation was similar in immature and mature hearts, yet the time required for basal tone to recover by 50% was approximately 100% greater in immature hearts (P less than 0.05). Immature aortic rings, stretched to their optimal resting tensions and contracted with EC85 doses of prostaglandin F2 alpha, displayed a significantly lower EC50 (7.7 x 10(-5) M) than mature rings (1.1 x 10(-4) M, P less than 0.05). The maximum percent response to adenosine was greater in immature vessels (64 +/- 1 vs. 54 +/- 0.4%, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

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