DECAVANADATE POSSESSES ALPHA-ADRENERGIC AGONIST ACTIVITY AND A STRUCTURAL MOTIF COMMON WITH TRANS-BETA FORM OF NORADRENALINE

Decavanadate, an inorganic polymer of vanadate, produced contraction o f rat aortic rings at a relatively high concentration compared to phen ylephrine, an agonist of alpha-adrenergic receptor. This effect was bl ocked by two known alpha-adrenergic receptor antagonists, prazosin and phenoxybenzamine. Decavanadate, formed by possible dimerization of V- 5 under acid conditions, possessed a structural feature of two pairs o f unshared oxygen atoms at a distance of 3.12 Angstrom, not found in i ts constituents of V-4 or V-5. A structural motif of O..O..O using suc h oxygen atoms is recognized in decavanadate. This matches with a simi lar motif of N..O..O that uses the essential amino and hydroxyl groups of the side-chain and the m-hydroxyl group in trans-beta form of nora drenaline. The interaction of such a structural motif with the membran e receptor is likely to be the basis of the unusual noradrenaline-mimi c action of decavanadate.