Paraquat-induced changes in the rate of collagen biosynthesis by rat lung explants

Paraquat, bipyridilium herbicide know to cause pulmonary fibrosis, was injected IP into rats. The rate of synthesis of collagen by lung minces from these and control rats was evaluated by measuring the rate of synthesis of hydroxyproline, a specific marker for collagen in lung. Synthesis was measured by incubating lung minces with radioactive proline for various amounts of time, after which proline specific activity and labeled hydroxyproline were determined. The size of the proline pool within the lung minces was significantly elevated in minces from rats that had been injected with paraquat, thus causing the specific activity of the [3H]proline precursor to be lower in these lungs than in those from control animals. Lung minces from rats administered paraquat made more collagen than did those from uninjected controls. The actual increase in rate of collagen synthesis correlated well with other independent estimates of paraquat-induced damage to the lungs.