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^oC 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.