Effects of purines and pyrimidines on the rat mesenteric arterial bed.

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Abstract
The effects of the purines, adenosine 5'-triphosphate (ATP) and guanosine 5'-triphosphate (GTP), and the pyrimidines, uridine 5'-triphosphate (UTP), cytidine 5'-triphosphate (CTP), and thymidine 5'-triphosphate (TTP), on vascular resistance were investigated in the rat mesenteric arterial bed. In preparations at basal tone, these agents produced dose-related vasoconstriction with a potency order of ATP greater than CTP greater than UTP much greater than TTP = GTP. When tone was raised with norepinephrine (30 microM), these agents caused dose-related vasodilatation with the potency order of UTP = ATP greater than TTP = GTP. CTP did not elicit vasodilatation. Removal of the endothelium with sodium deoxycholate resulted in an increased responsiveness of the mesenteric bed preparation to the vasoconstrictor effects of each of the purines and pyrimidines tested. The selective P2 X-purinoceptor-desensitizing agent alpha,beta-methylene ATP inhibited vasoconstrictor responses to ATP and to CTP but had no effect o...