It appears, from the investigations in other laboratories, that the anemia observed in cases of lead poisoning is due to destruction of blood rather than to diminished production of blood. The method of poisoning cells in vitro with lead was adopted in order to study this phenomenon, and distinct effects were thereby obtained, even when only 0.001 mg. of lead is added to approximately 5 billion washed red corpuscles. In order to obtain optimum results the usual dosage employed was ten times this or 0.01 mg. per 5 billion cells. The following changes were observed in cells so treated.
1. Such a marked increase in the resistance to hypotonic salt solution develops that complete hemolysis does not occur until the cells are exposed to a saline solution of 0.05 per cent. Untreated cells are completely hemolyzed in 0.25 or 0.225 per cent saline.
2. This reaction is quantitative and varies with the concentration of lead used. Under the conditions of our experiments this phenomenon seems to be unique. The effects of arsenic are very slight in comparison.
3. While from this reaction it may be concluded that lead increases cellular resistance, it also appears that it shortens the life of blood cells. This may be demonstrated by the much more rapid appearance of hemolysis than normal when the cells are merely allowed to stand in Ringer solution of any dilution.
4. In rabbits with acute lead poisoning these same phenomena may be noted in vivo.
5. Both phenomena may be changed in vitro by varying the time and temperature of the reaction and the concentration of lead, as Fici has already pointed out.
6. If normal cells stand in Ringer solution for 6 hours something diffuses into the solution which largely reduces the action of lead. After repeated washing these cells react with lead in the usual manner.
7. Small amounts of serum react with lead and eliminate its effects. Red blood cells, treated with a mixture of lead and blood serum, show normal hemolysis in hypotonic salt solution.
8. When lead is added to whole blood the only evidence of this neutralization is a marked decrease in the intensity of the reaction. This is probably explained by the fact that since both serum and cells are present together, the lead reacts with both simultaneously. This in turn explains how the reaction may occur in vivo.
9. The change in hemolysis does not appear in the blood of all species of animals. In the species in which it does occur, anemia and stippling of the red cells also tend to develop readily during lead intoxication.
10. In vitro, cells which have been exposed to lead are far more fragile than normal blood cells. Slight trauma causes them to hemolyze. In vivo this is probably an important causal factor in the increased destruction of blood and in the anemia of acute lead poisoning.
11. The serum of a rabbit which has been immunized to human blood, causes more rapid and complete hemolysis in cells treated with lead than in the control cells. No satisfactory explanation for this has been found.