Pulmonary hypertension in rats. 1. Role of bromodeoxyuridine-positive mononuclear cells and alveolar macrophages.

The role of activated cells determined by staining with bromodeoxyuridine (BrdU) and the role of alveolar macrophages as a source of cytokines were investigated in monocrotaline (MCT)-induced pulmonary hypertension (PH) in rats. BrdU was mainly incorporated by mononuclear cells; their number increased strikingly prior to the development of PH. Cytokines such as interleukin (IL)-1, IL-6 and tumor necrosis factor were produced during the development of PH. The amount of IL-6 showed significant correlation (p < 0.05) with the number of BrdU-positive cells, which, in turn, correlated with the extent of PH. These results indicate that BrdU-positive cells and cytokines produced by alveolar macrophages may play an important role in the pathogenesis of MCT-induced PH in rats.