Abstract
Various adenosine analogues phosphorylated or not, modified at the purine ring level or in the carbohydrate moiety, have been tested for their ability to induce a vasoconstriction in the arterio-arterial vascular bed of the trout gill. The structural integrity of the purine ring and the N-glycosidic bond are required for activity. The anti conformation of the molecule is preferable to the syn conformation. The basicity and/or the hydrogen bonding capabilities at the 6-position are important for the potency of the molecule. Substitutions which decrease the basicity of the 1-position decrease the activity and substitutions which reinforce the basicity (2-Cl adenosine) increase it. Alterations of the furanose ring conformation and the reduction of the hydrogen bonding capabilities of the 2′- and 3′-hydroxyls decrease the potency of the compound. Some substitutions in the 5′-position intensify the haemodynamic response. Thus, 5′-ethyl carboxamide adenosine is one order of magnitude more potent than adenosine. The addition of more than one phosphate in 5′-position (ADP, ATP) favours the effectiveness of the compound but a further elongation of the phosphate chain does not improve its potency. The α-β configuration of the phosphate chain is essential for the physiological effect. IMP, adenylosuccinate and all cyclic necleotides are devoid of haemodynamic activity. These results sustain the hypothesis of the presence of specific vascular purinergic receptors in the trout gill.
Published Version
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