NGF and Right ventricular hypertrophy: Furthermore, in a rat model of right ventricular hypertrophy, it was reported that NGF protein expression was increased in conjunction with ET-1 mRNA expression in the right ventricle, and that sympathetic nerve fiber density in the right ventricle was also markedly increased (Kimura et al., 2007), indicating that the ET-1/NGF pathway is involved not only in cardiac development but also in pathological states.