Ultrasound as a novel method for selective damage of endocardial endothelium

Damage of endocardial endothelium by mechanochemical methods in isolated cardiac muscle induces typical changes in the contractile performance of the myocardium. Functional and morphological features of isolated cat papillary muscles treated with ultrasound, a new technique for in vitro damage of endocardial endothelium, were compared with damage by Triton X-100. Treatment with either short bursts of continuous wave ultrasound (25 W; 1.05 MHz) or with 1-s immersion in 0.5% Triton X-100 resulted in an irreversible abbreviation of twitch contraction with concomitant decrease in total peak twitch tension but without significant changes in maximal unloaded velocity of shortening. Decrease of total peak isometric tension was significantly more pronounced after Triton X-100 administration. Scanning electron microscopy showed an extracted endothelium following immersion in Triton X-100 and a nearly complete desquamated surface after ultrasound. Fluorochromes in muscles treated with Triton X-100 or ultrasound did not enter myocytes, which maintained a normal ultrastructure. After Triton X-100, more endocardial fibroblasts were labeled and showed ultrastructural damage than after ultrasound. Ultrasound constitutes a powerful technique for selective in vitro damage of endocardial endothelium. The technique is also suitable for experimental in vivo intracardiac application.