High uptake in the erythrocytes and the spleen of the quaternary dipyridylium salt paraquat injected intravenously in hypotonic solutions.

Intravenous injections of the quaternary dipyridlium salt paraquat (14C-labelled) dissolved in solutions of low tonicity result in a high uptake in the erythrocytes and concomitantly also in the spleen (red pulp), the latter being probably due to phagocytosis of paraquat-containing erythrocytes by the reticuloendothelial system. Higher tonicities of the injected solutions result in a low uptake and the same applies to oral, intraperitoneal and subcutaneous injections. Paraquat was present in the erythrocytes in a non-metabolized form without being bound to membranes or proteins. The uptake in the erythrocytes was not influenced by alterations of the pH or by the preparation of a charge-transfer complex with serotonin in the injection solutions. Chemical alterations of the paraquat in the injection solutions could not be detected. In vitro the uptake of paraquat in the erythrocytes was higher in the haemolysed (and then reconstituted by adding sodium chloride) erythrocyte-ghosts than in the non-haemolysed erythrocytes, as shown by incubations at various tonicities. It is proposed that the intravenous injections of paraquat in hypotonic solutions temporarily alter the membranes of the erythrocytes in the blood-stream and make them permeable to paraquat, possibly, as judged from the in vitro experiments, only during a short period of partial haemolysis. The distribution studies also showed a retention of paraquat in the lungs. In addition paraquat was accumulated in the melanin of the tissues.