The aim of the study was to investigate the expression levels of endothelin-1 (ET-1) and ET_A and ET_B receptors (ET_A-R and ET_B-R) in porcine mitral valves and associate the transcription levels to age, leaflet location and deposition of mucopolysaccharides (MPS). Tissue samples from the chordal and interchordal insertion area of the anterior mitral valve leaflet from 11 sows (=2 years of age) and 10 slaughter pigs (approximately 6 months old) were obtained and the relative gene expression levels of ET-1, ET_A-R and ET_B-R measured by semi-quantitative real-time PCR. A separate tissue sample was taken for histopathological grading of MPS deposition. The transcription levels of ET-1 (P < 0.0001) and ET_A-R (P < 0.0004) were significantly higher in leaflets from the sows compared with slaughter pigs. The gene expression of ET_B-R was not associated to age (P = 0.38), but increased in chordal insertion areas compared with inter-chordal areas (P = 0.01). The expression of ET-1 and ET_A-R mRNA did not differ significantly between the two leaflet locations. The valve leaflets from sows had a significantly increased degree of MPS deposition compared with slaughter pigs upon histological examination (P = 0.04). In conclusion, an age-related valvular degeneration is observed in porcien mitral valve leaflets and ET-1 is suggested to be involved through action of both ET_A and ET_B receptors.