Adenosine deaminase in stroma-free hemoglobin solution is not responsible for coronary vasoconstriction

Erythrocytes contain a high concentration of cytosolic adenosine deaminase and this enzyme activity is present in preparations of stroma-free hemoglobin (SFHS). The documented vasoconstrictor activity of SFHS preparations does not appear to be due to interference with endogenous adenosine-mediated mechanisms, because removal of greater than 80% of adenosine deaminase activity failed to affect the vasoconstrictor potency of SFHS preparations. We have also demonstrated the presence of a contractility-depressant activity in SFHS when the latter was added to aqueous buffer perfusing rat Langendorff-hearts. This activity is diminished in phosphocellulose-purified preparations with reduced adenosine deaminase activity but is not necessarily causally related to this enzyme.