This in vitro study was undertaken to investigate the effects of adenyl purines in human uterine myometrium and uterine arteries. Segments of uterine myometrium and uterine arteries obtained at hysterectomy were isolated and mounted in tissue chambers. The muscle activity was recorded by polygraph. Adenyl purines agonists, such as adenosine, N-[(R)-1-methyl-2 phenylethyl]-adenosine (R-PIA) and 5-N-ethylcarboxamide adenosine (NECA) produced concentration-dependent contraction in human uterine myometrium. The potency order was NECA = R-PIA > adenosine. Adenosine A1 receptor antagonist: 1, 3-dipropyl-8-cyclopentylxanthine (DPCPX) blocked the effect of adenosine in human uterine myometrium. Otherwise, adenyl purines induced dose-dependent relaxation in human uterine artery precontracted by phenylephrine (PE, 10(-5)M). The potency gradient was NECA > R-PIA > adenosine; the results indicate adenyl purine induces uterine myometrium contraction via A1 receptor. However, adenosine causes uterine artery relaxation by A2 receptor.