Inhibition of paraquat accumulation in rat lung slices by a component of rat plasma and a variety of drugs and endogenous amines

The accumulation of paraquat by slices of rat lung has been shown to be inhibited in vitro by the addition of rat plasma. For a given concentration of plasma, inhibition was constant with time and the amount of inhibition increased with increasing concentration of plasma. This suggests that there are components of rat plasma which inhibit paraquat accumulation by rat lung slices in a concentration-dependent manner. An ultrafiltrate of plasma also inhibited paraquat uptake, indicating that the inhibitor is a small molecular weight compound. A number of endogenous amines including noradrenaline, 5-hydroxytryptamine and histamine have been shown to reduce the concentration of paraquat accumulated into lung slices, as have several other drugs including imipramine, propranalol, burimamide and betazole. The relevance of these findings to the prevention of paraquat accumulation by lung is discussed.