Urokinase-type plasminogen activator in alveolar macrophages and bronchoalveolar lavage fluid from normal and smoke-exposed hamsters and humans.

Our purpose was to identify and characterize plasminogen activator (PA) activity in alveolar macrophages (AMs) and lower respiratory tract fluid from hamsters and humans. Freshly harvested hamster AMs had barely detectable PA intracellularly and no detectable activity in concentrated lavage fluid. PA secretion was detected in conditioned media of hamster AMs. Secretion was enhanced sixfold by phorbol myristate acetate (PMA) and suppressed by dexamethasone. In contrast to hamsters, PA activity was readily detected in lysates of freshly harvested human AMs and lavage fluid. However, secretion of PA by human AMs was not detected, and neither PMA nor dexamethasone affected PA activity. PA from hamster or human AMs has a urokinase-type enzyme with molecular weights of 49,000 or 55,000, respectively. Cigarette smoking did not alter PA activity by hamster or human AMs.