Repeated lung injury due to alpha-naphthylthiourea causes right ventricular hypertrophy in rats

Acute lung injury due to alpha-naphthylthiourea (ANTU) is associated with increased permeability edema, transient pulmonary hypertension, and increased vascular reactivity. We sought to determine whether repeated administration of ANTU caused right ventricular hypertrophy. Rats were injected weekly for 4 wk with ANTU or an equivalent volume of the vehicle Tween 80. Rats injected repeatedly with ANTU in doses of 5-10 mg/kg body wt had increased ratios of right ventricular to left ventricular plus septal weights. The right ventricular hypertrophy in ANTU-treated rats was associated with right ventricular systolic hypertension. Repeated injections of ANTU also caused transient pulmonary edema after each dose, as evidenced by increased wet-to-dry lung weight ratios after 4 h, which returned to normal by 24 h. Lungs isolated from ANTU-injected rats had greater pressor responses to hypoxia and to angiotensin II than lungs from Tween 80-injected rats. Pressure-flow curves of isolated lungs, arterial blood gases, and hematocrits were similar in rats treated repetitively with ANTU or Tween alone. Lung histology was also similar in ANTU and control lungs, as were measurements of arterial medial thickness and ratios of numbers of arteries/100 alveoli, indicating that substantial vascular remodeling had not occurred. Thus, four weekly ANTU injections in rats caused right ventricular hypertrophy, probably due to pulmonary hypertension. We speculate that the pulmonary hypertension was due, at least in part, to sustained vasoconstriction, which somehow resulted from repeated acute lung injury.