TRANSMURAL-STIMULATION OF MESENTERIC-ARTERY IN THE PRESENCE OF CROSS-LINKED HEMOGLOBIN PRODUCES A COMPOUND WITH CHROMATOGRAPHIC CHARACTERISTICS SIMILAR TO DOPAMINE

When sympathetic nerve endings in isolated canine mesenteric arteries were depolarized electrically, a compound appearing to be dopamine, wa s released frequency-dependently. Production of the putative dopamine occurred only in arteries exposed to alpha alpha cross-linked hemoglob in. The aim of this study was to determine whether this compound was a uthentic dopamine. Several chromatographic characteristics of the unkn own compound were identical to those of dopamine; adsorption onto Sep- Pak C-18 cartridges, and isographic elution on a reversed-phase HPLC c olumn. However, further analysis revealed that the compound did not ad sorb onto neutral alumina or onto cationic-exchange resin as did dopam ine, and that its voltammetric properties were not identical to those of dopamine. Subsequently, the compound was found to be produced in Kr ebs-Ringer solution in the absence of artery, provided alpha alpha cro ss-linked hemoglobin, oxygen and an electric current were supplied. Si milar results were obtained when other proteins were substituted for a lpha alpha cross-linked hemoglobin. It is concluded that the compound released from mesenteric artery by alpha alpha crosslinked hemoglobin was not dopamine.