FEMORAL VASCULAR RESPONSES TO PURINE ANDPYRIMIDINE DERIVATIVES: RELEASE OF5-HYDROXYTRYPTAMINE BY PURINE DERIVATIVESIN ISOLATED, CROSS-CIRCULATED RAT HINDLIMB*

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Abstract
The mode of actions of the purines (adenosine, ATP guanosine and GTP) and the pyrimidines, (cytidine, CTP, thymidine, TTP, uridine and UTP) was studied in the isolated hindlimb preparation of the rat. A single injection of adenosine, ATP, GTP or UTP into the femoral artery induced a biphasic response, a prominent vasoconstriction preceded by a transient vasodilatation; guanosine and uridine caused only a vasoconstriction. Cytidine, CTP, thymidine and TTP were almost ineffective on the vascular bed. The vasoconstrictor responses to adenosine, ATP, guanosine and GTP were effectively antagonized by either methysergide or reserpine; those to uridine and UTP were not modified by methysergide or phentolamine. Adenine, D-(-)-ribose and hypoxanthine had no effect on the vascular bed. The 5-hydroxytryptamine (5-HT) release from the hindlimb was fluorometrically determined. Apparently the vasoconstriction caused by ATP, adenosine, GTP snd guanosine is due to the release of 5-HT from their stores and purine nucleotides and nucleosides are capable of releasing 5-HT.

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