RECOVERY OF Ca²⁺-ATPASE ACTIVITY OF CARDIAC MYOCYTE WITH BIVENTRICULAR SUPPORT IN THE CANINE FAILING HEART

Abstract

Prolonged normothermic global ischemia in the canine model is generally fatal. To determine whether Ca²⁺-ATPase activity in such injured cardiac myocyte is recoverable with biventricular assist support (BVAS), we subjected 15 canines to 45 minutes of global ischemia at normothermia. After ischemia and further 20 minutes of reperfusion (G2), the animals were supported for 3 hours with BVAS (G3). Mean BP, developed pressure and LVmaxdp/dt in G2 significantly reduced compared with control (G1) and those in G3 were significantly recovered after 3 hours with BVAS compared with G2. Kinetics of Ca²⁺-ATPase activity of the failing cardiac myocyte with BVAS was estimated using a lead citrate method. Electromicroscopic findings of Ca²⁺-ATPase activity in G2 showed noactivities in sarcoplasmic reticula (SR) and myofilaments (MF) but showed less activity in mitochondria (MT) compared with G1. At 3 hours with BVAS in G3, Ca²⁺-ATPase activity of MT was recovered but those of SR and MF remained low. In conclusion, our data indicate that BVAS makes a contribution to the recovery of Ca²⁺-ATPase activity of MT in the failing canine heart due to normothermic global ischemia for 45 minutes.