Abstract
Acid-base imbalances may provoke contractile dysfunction in the human newborn. We compared isometric contraction of adult and neonatal myocardium during changes in extracellular pH. Preparations of small ventricular muscle (VM) from 20 adult dogs and 19 neonates (age 1-7 days) were mounted in a muscle chamber and were superfused with Tyrode's solution (36°). Isometric force was monitored. After 1 hour equilibration at control pH (7.35), HCO3− concentration was varied while maintaining Na+ isoosmolarity. Adult VM developed peak active force per cross sectional area (pa/XSA) of 1.19 ± .26g/mm2 at pH 7.35 (control). Acidosis (Aci) (pH 6.8-7.1) decreased pa/XSA 11%, while alkalosis (Alk) (pH 7.5-7.7) increased pa/XSA 10%. Time to peak active force (TTP) was 0.22 ± 0.01 sec in pH 7.35 and decreased in both Aci and Alk. Rate of force development (dp/dt; 2.55 ± 0.28g/sec) was unaffected by Aci but increased 16% (p≤0.05)in Alk. The pa/XSA from RV of neonatal dogs was lower (0.18 ± 0.04g/mm2) but responded similarly to changes in pH. dp/dt was 1.37 ± 0.19g/sec and in contrast to adult VM decreased 14% (p≤0.05) in Aci. TTP (0.17 ± 0.02 sec) was decreased by Alk 18% (p≤0.05) and unaltered by Aci. Our data demonstrates age-related alterations in mechanical responses during changes in extracellular pH. (Sup. by March of Dimes and American Heart Association, Fla. Suncoast Affiliate.)
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Ezrin, A., Myerburg, R., Bassett, A. et al. 246 EFFECTS OF ALTERATIONS IN EXTRACELLULAR pH ON CARDIAC MUSCLE OF ADULT AND NEONATAL DOGS. Pediatr Res 12 (Suppl 4), 404 (1978). https://doi.org/10.1203/00006450-197804001-00251
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DOI: https://doi.org/10.1203/00006450-197804001-00251