Serotonin transmembrane transporter is down-regulated in late-stage canine degenerative mitral valve disease

Abstract Objective To compare expression of the serotonin transmembrane transporter (SERT) in normal, early-stage degenerative, and late-stage degenerative canine mitral valve disease. Animals 24 post-mortem canine mitral valves. Methods SERT expression was determined in canine normal ( n  = 8), early-stage degenerative ( n  = 8), and late-stage degenerative ( n  = 8) mitral valves by immunohistochemistry (IHC) and immunoblot (IB) analyses. Results SERT was expressed in valve interstitial cells of all layers of normal and early-stage degenerative mitral valves based on IHC. SERT was markedly down-regulated in valve interstitial cells, but not valve endothelial cells, of late-stage degenerative mitral valves. SERT expression was significantly decreased in late-stage compared to normal and early-stage degenerative mitral valves based on IB analysis ( P Conclusions Down-regulation of SERT expression occurs in valve interstitial cells of late-stage, but not early-stage, canine degenerative mitral valves. Down-regulation of SERT could enhance the recently speculated role of serotonin in canine DMVD by decreasing serotonin metabolism and increasing interaction with its receptor. Down-regulation of SERT likely does not play an initiating role in canine DMVD since it does not occur in early-stage disease.