The role of endocardial endothelium on inotropic effect of adrenaline on the isolated right ventricle of rat heart

Abstract

It is known that adrenaline ( L - epinephraie) produces positive inotropic effect on isolated right ventricle of rat heart. Purpose : The aim of our study was to investigate inotropic effect of adrenaline on the isolated right ventricle of Wistar rat heart in the presence and absence of endocardial endothelium. Methods : Endocardial endothelium was damaged by immersion for I s of right ventricle with Triton X-100 dissolved in a Crebs-Ringer solution at 20°C followed by rapid abundant wash in Tyrode's solution at 35°C. Each ventricle was put on a boot electrode and than placed in a bath with Tyrode's solution bubbled with 95% O 2 /5% CO 2 The volume of the bath was 25 ml, pH=7.4 and it's temperature was kept on 37°C. Contractions were induced with square wave impulses of twice the diastolic threshold and a duration of 5 ms at a frequency on I Hz. The contractions were recorded via an isometric transducer (sensitivity of 0.05 g/cm) into a microdynarnometer (7050 Ugo Basile). After stabilization period of 30 min adrenaline (Sigma, USA), in a dose 10 5 mol/l, which produced maximal positive inotropic effect, was added into the bath and contractions were recorded continuously for another 60 min. Results : The positive inotropic effect of adrenaline in both groups was expressed immediately after the application. In the group with intact endocardial endothelium the maximal inotropic effect was reached in 2 nd min. (92% higher than in the controls, p<0.05). In the group with damaged endocardial endothelium it was reached in 3 rd min. (183% higher than the controls, p<0.05). The inotropic effect of adrenaline was approximately 100% higher in the experimental group without endocardial endothelium.