Background and aim of the study: Little is known of the local role of nitric oxide (NO) in heart valves in relation to heart valve diseases. The study aim was to examine NO release and the expression of both endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS) in relation to early local changes in porcine mitral valves.
Methods: A histological evaluation of mitral valve leaflets from slaughter pigs and sows was made, and the expression of eNOS and iNOS protein measured using immunohistochemistry. Furthermore, mRNA levels of eNOS and iNOS were measured using real-time RT-PCR. A calibrated NO-specific electrode was used to measure local NO release in specific regions of the anterior mitral leaflet from slaughter pigs and sows interchordally at the tip of the leaflet (region A), at the chordal insertion (region B), and at the center of the leaflet (region C).
Results: Leaflets from sows had an increased accumulation of mucopolysaccharides (MPS) compared to those from slaughter pigs. Furthermore, mRNA levels of eNOS and iNOS were significantly increased in region C due to very high levels of expression in some sow leaflets. NO release in the sow mitral valve leaflet was increased in regions B and C compared to that in region A.
Conclusion: The relative distribution of NO release is increased in regions of porcine mitral valve leaflets with deposition of MPS and defraction of the valve structure, which may reflect changes in both eNOS and iNOS expression.