1.The epinephrin test was performed in 12 normal subjects and 63 patients with various hematologic disorders to evaluate its role in the diagnosis of hypersplenic syndromes and aplastic anemias. Attention was directed solely to the early phases of the reaction, that is to the pre-adrenocortical stimulatory effect, which has been claimed to reflect the functional activity of the spleen and bone marrow.

2. The epinephrin response in normal subjects was characterized by transitory pancytosis. Leukocytosis and thrombocytosis were conspicuous features whereas erythrocytosis and reticulocytosis were not regularly seen. Leukocytosis was due to an increase of mature forms of neutrophils, lymphocytes, monocytes and eosinophils. The Arneth count did not show any significant variation after epinephrin. There was no correlation in different cases between the degree of hemopoietic response and the degree of rise of blood pressure, although in each case the time of maximum cellular response usually ran parallel to the time of maximum rise of blood pressure.

3. The response in splenectomized individuals was essentially similar to or slightly greater than that seen in normal subjects. In splenomegalic conditions there was no correlation between the degree of splenic contraction and the degree of hemopoietic response.

4. Results of epinephrin injection into the splenic artery showed that the increase of cellular elements was in general pancellular in type, and not confined to any particular cell deficient in the peripheral blood; it was obviously independent of the nature and degree of peripheral cytopenia.

5. The splenic contraction following epinephrin may possibly be due to a marked constriction of the splenic artery and in its intrasplenic branches with the resultant passive deflation of the organ.

6. In each case there was a close correlation between the epinephrin response and the functional activity of the bone marrow.

7. The epinephrin test per se is not diagnostic of any clinical condition. In the hypersplenic syndromes interpretation of negative tests may actually be misleading. At most, the test provides indirect corroborative evidence regarding the functional status of the blood forming tissues and to some extent of the "reservoir" of blood cells present not only in the bone marrow, but in various tissues and organs throughout the body. The exact degree of splenic participation in the epinephrin response is not known, but our studies indicate that it is minimal.

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