Preliminary characterization of vasocontractile activities in erythrocytes

The vasocontractile activities of washed red cell preparations hemolyzed by various methods were studied in vitro using isolated canine basilar arteries. Significant contractions were induced by each preparation. The maximum strength of contraction attained by the various preparations was similar. The contractile activity appeared to be dose-related, and molecular exclusion chromatography demonstrated that the activity migrated with the fraction of approximately 40,000 to 45,000 molecular weight. The vasocontractile effect of the active fraction was sustained in vitro when tested against basilar artery, but was inactive in peripheral arterial preparations. Preliminary biochemical characterization indicates that the contractile activity resides in a protein. Enzymatic digestion of the crude fraction appears to enhance the contractile activity significantly, and this observation suggests a possible mechanism for the delayed onset of ischemic symptoms encountered in the clinical situation.