FORMATION OF HYDROXYTYRAMINE FROM TYRAMINE IN THE ADRENAL GLAND

摘要

References(19) The possibility that adrenaline may arise from tyramine in adrenal gland was first postulated by Ewins and Laidlaw (1) in 1910. This was supported by the perfusion data of Nikolaeff (2) and the slice experiment of Schuler (3), Devine (4) and Holtz (5) which demonstrated the conversion of adrenaline from tyramine, but not from tyrosine, dihydroxyphenylalanine (dopa), or phenylalanine. However, since the experiment of Halle (6) in 1906, Guggenheim (7), Knoop (8), Rosenmunt and Dornsaft (9) asserted that tyrosine might be an effective precursor of adrenaline. In 1938, previous studies (10, 11) in our laboratory presented the evidence for the existence of this pathway, and later this was confirmed by the isotopic data of Udenfriend et al. (12) which established that adrenaline was formed from tyrosine, but not from tyramine in vivo. Recently the reaction of hydroxytyramine to noradrenaline has been demonstrated to be catalysed by an enzyme requiring FAD and Fe++ (13). Thus it is generally assumed at present that the following reaction sequence takes place as the main pathway to form adrenaline.Tyrosine→Dopa→Hydroxytyramine→Noradrenaline→AdrenalineMore recently it has been found in our laboratory that tyramine was oxidized to hydroxytyramine in blood and liver of rabbits (14, 15). This observation suggests the possibility that tyramine might be also a precursor of adrenaline, if the same oxidation process would be demonstrated to occur in adrenal gland. In the present paper the results of a preliminary survey of this metabolic pathway are described, together with the properties of the enzyme responsible for the oxidation of tyramine to hydroxytyramine in adrenal gland.