The protective effect of lisinopril on membrane-bound enzymes in myocardial preservation

A number of studies have reported that oxidant stress reduces the activity of isolated Na+ - K+ ATPase and Ca2+ ATPase which are known to affect the c ell membrane integrity. The aim of the study is to determine whether the ad ministration of lisinopril is able to protect the membrane-bound enzyme lev els in isolated guinea pig hearts and also ascertain whether or not a relat ionship exists between oxygen free radicals and membrane bound Na+ - K+ ATP ase and Ca2+ ATPase. Forty guinea pig hearts were studied in an isolated Kr ebs-Henseleit solution-perfused Langendorff cardiac model. In all groups ca rdioplegic: arrest was achieved by administering St. Thomas' Hospital cardi oplegic solution (STHCS). Group 1 (control, n = 10) received only STHCS. Gr oup 2 (n = 10) were arrested with lisinopril (1 mu mol 1(-1)) added STHCS, Group 3 (n = 10) were pretreated with oral lisinopril (0.2 mg kg(-1) twice a day) for 10 days and then arrested with STHCS. Group 4 were also pretreat ed with oral lisinopril (0.2 mg kg(-1) twice a day for 10 days), arrested w ith STHCS and reperfused with lisinopril added to Krebs-Henseleit solution (1 mu mol 1(-1)). Hearts were subjected to normothermic global ischaemia fo r 90 min and then reperfused at 37 degrees C. Pretreatment and addition of lisinopril in the reperfusion buffer improved the levels of membrane-bound enzymes. When the treated groups were compared with control hearts, the bes t results were achieved in group 4. The Na+ - K+ and Ca2+ ATPase levels inc reased from 466.38+/-5.99 to 560.12+/-18.02 and 884.69+/-9.13 to 1287.71+/- 13.01 nmolPi mg(-1) protein h(-1) respectively (p < 0.05). These results su ggest that lisinopril protects the cell membrane integrity and lessens free radical-induced oxidant stress. Copyright (C) 2000 John Wiley & Sons, Ltd.