Possible relationship between mechanical response, action potential repolarization and Na/Ca exchange in myocardium of normotensive (NWR) and spontaneously hypertensive rats (SHR).

Electrical and mechanical restitution was tested in ventricular preparations of adult NWR and SHR. As in atrial preparations we found a positive correlation between force and action potential duration in the late repolarization phase (APD90), though the effect of test interval prolongation on APD90 was less in papillary muscle compared to atrial preparations. These relationships as well as the differences between NWR and SHR-responses may be interpreted in part by the altered activity of the Na/Ca exchange.