Increased expression of endothelin B receptor in static stretch exposed porcine mitral valve leaflets.

Abstract The aim of this study was to evaluate the effect of mechanical stretch on the expression of ET-1 and ET A - and ET B -receptors in porcine mitral valve leaflets. Leaflet segments from 10 porcine mitral valves were exposed to a static stretch load of 1.5 N for 3.5 h in buffer at 37 °C together with matching control segments. Subsequently, the mRNA expression of ET-1, ET A -R and ET B -R was measured by real-time RT-PCR in the chordal insertion areas. The analyses showed an increased transcription of ET B -receptors in stretch-exposed leaflet segments compared to unstretched segments median 2.23 (quartiles 1.37 and 2.70) vs. median 1.56 (quartiles 1.38 and 2.17, P  = 0.03) whereas the mRNA expression of ET A -receptors ( P  = 0.90) and ET-1 ( P  = 0.51) remained unchanged. Stretch increased the expression of ET B -receptors in porcine mitral valve leaflets. The finding could lead to a better understanding of the pathogenesis of myxomatous mitral valve disease.