Human resistance arteries were obtained from specimens of omentum and subcutaneous fat removed at surgery. They were studied in vitro by use of a myograph technique to determine the effects of purines on the arteries. 2. In preparations where tone had been raised with noradrenaline, low concentrations (1 nM-1 microM) of adenosine triphosphate (ATP) and 2-methylthioATP, but not alpha,beta-methyleneATP, produced concentration-dependent relaxation. There was a lack of relationship between the relaxation response to acetylcholine and that to ATP. 3. In preparations under basal tone, high concentrations (1 microM-1 mM) of ATP, 2-methylthioATP and alpha,beta-methyleneATP produced concentration-dependent contractions. 4. The rank order of potency of the purine nucleotide analogues for the relaxation response was 2-methylthioATP > ATP > alpha,beta-methyleneATP and for the contractile response it was alpha,beta-methyleneATP > ATP = 2-methylthioATP. 5. Adenosine produced concentration-dependent relaxation in preparations under raised tone and was less potent than ATP but did not produce contraction in preparations at basal tone. Relaxation responses to adenosine, but not to ATP, were antagonized by 8-phenyltheophylline. 6. These results indicate the presence of vasodilator P2y- and P1-purinoceptors and vasoconstrictor P2x-purinoceptors on human resistance arteries isolated from omental and subcutaneous sites.
