The Effect of Intravenous Histamine Administration on the Level of the White Blood Count in the Peripheral Blood

1. By simultaneously sampling venous and arterial blood by cardiac catheterization or vessel cannulation, the number of leukocytes entering and leaving the lungs was observed in 12 patients on 14 occasions.

2. The intravenous administration of histamine phosphate in doses of 0.1 to 0.3 mg. (as base) over 10 to 60 seconds, was accompanied by a prompt decrease in leukocyte number in the arterial blood 20 to 60 seconds before the venous white cell count fell. This was interpreted as demonstrating that the leukocytes were removed from tine peripheral blood in the pulmonary circulation. The granulocytic series appeared to be more involved in the leukopenia, although a similar but less apparent change was noted in the agranulocytes.

3. The leukopenia persisted for 40 to 180 seconds following which the arterial leukocyte count exceeded that in the venous blood indicating a return of leukocytes from the lungs into the peripheral circulation.

4. The intravenous administration of histamine also resulted in an immediate decrease in clotting time as determined both by glass and siliconed tube technics.

5. The intravenous injection of histamine affords a relatively simple technic to study one type of leukocyte removal mechanism present in the pulmonary circulation.