Abstract
The mechanisms which account for the normal positive staircase response to increasing contraction frequency remain unclear. It has been postulated previously that transarcolemmal sodium-calcium (Na-Ca) exchange may be important for the generation of a normal force-frequency response (FFR). To test this hypothesis, we performed FFR before (Pre) and 60 minutes after (Post) inhibition of Na-Ca exchange by amiloride (1.0 mM) using isometrically contracting right ventricular papillary muscles from immature (I; 14-21 days of age) and adult (A) rabbits. Results for maximal rate of tension development (dT/dt; gm/sec) obtained during the Pre and Post FFR are tabulated below (mean±SE):
Thus, under these conditions, the positive staircase response to increasing contraction frequency was preserved in the presence of amiloride in both age groups. These results suggest that Na-Ca exchange is not critical for the generation of the normal FFR in I or A rabbit myocardium.
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Artman, M., Crump, D., Boerth, R. et al. 78 INHIBITION OF SODIUM-CALCIUM EXCHANGE BY AMILORIDE: EFFECTS ON THE FORCE-FREQUENCY RESPONSE IN IMMATURE AND ADULT MYOCARDIUM. Pediatr Res 19, 123 (1985). https://doi.org/10.1203/00006450-198504000-00108
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DOI: https://doi.org/10.1203/00006450-198504000-00108
