Regulation of vascular tone by UTP and UDP in isolated rat intrapulmonary arteries

Vasoconstrictor and vasodilator responses of isolated rat intrapulmonary arteries to the pyrimidine nucleotides UTP and UDP were evaluated and compared with vascular responses to ATP and its analogues. UTP and UDP (1-500 mu M) were equipotent in inducing concentration-dependent vasoconstriction, unaffected by the P2 receptor antagonists suramin (100 mu M) and Reactive blue 2 (50 mu M); ATP (10-500 mu M) produced weaker vasoconstriction. UTP and UDP lacked vasodilator activity, while ATP and its analogue 2-methylthio ATP evoked endothelium-dependent vasodilatation. These results indicate that UTP and UDP evoke vasoconstriction of rat intrapulmonary arteries whereas ATP is predominantly a vasodilator at the same arteries. Furthermore, the pharmacological profile of the native UTP/UDP receptor differs from that of the known P2Y(2), P2Y(4) and P2Y(6) recombinant receptors for pyrimidine nucleotides. (C) 1999 Elsevier Science B.V. All rights reserved.