CHRONIC PULMONARY-HYPERTENSION IN SHEEP - TEMPORAL PROGRESSION OF LESIONS

Scant data exist on the evolution of the lesions of pulmonary hyperten sion, This study establishes a model in sheep in which the left upper lobe (LUL) was rendered hypertensive by a systemic-pulmonary shunt whi le the rest of the pulmonary circulation remained normotensive. By exa mining lung tissue at 2 months and 1 1/2 years after shunting, we soug ht the temporal progression of pulmonary hypertensive lesions, In the hypertensive LULs (n = 5), many vascular lesions were seen in contrast to the absence of lesions in both the contralateral normotensive lung s (n = 5) and the ''control'' lungs from sheep which underwent thoraco tomy without shunting (n = 5), Vascular necrosis and vasculitis were p resent after 2 months (P < 0.01) but disappeared after 1 1/2 years. In contrast, intimal thickening was present after 1 1/2 years (n = 2, P < 0.01) but not significantly after 2 months, These intimal lesions of ten demonstrated increased cellularity staining positively for factor VIII, Plexiform lesions were present at 2 months (P < 0.05) but were m ore profuse after 1 1/2 years (P < 0.01). These findings are consisten t with an early vascular injury and a later remodeling or reparative p rocess in hemodynamic pulmonary hypertension. (C) 1996 Academic Press, Inc.