Norepinephrine and epinephrine in human erythrocyte plasma membranes

Acetone extract prepared from the plasma membranes of human erythrocytes contained substances which induced the contraction of the thoracic aortic strip of rabbit in vitro and caused blood pressure elevation in rat upon intravenous injection. The contractile response was inhibited by the α 1-adrenergic antagonist prazosin. By HPLC/electrochemical detection as well as radioenzymatic assay, large amounts of norepinephrine (NE) (14 ± 4 [SE] ng/ml packed cells) and epinephrine (E) (16 ± 2 ng/ml packed cells) were found in the extract. Using the same amounts as in the extract, we were able to demonstrate additive effect between NE and E. The possibility that erythrocyte membranes may play a role in the regulation of NE and E in circulation is suggested.