Adenosine triphosphate-evoked vascular changes in human skin: mechanism of action.

Adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), adenosine, adenine and inosine were injected intradermally into the backs of human volunteers. ATP, ADP and AMP evoked weal and flare responses in the skin in a dose dependent manner. The rank order of potency was ATP greater than ADP greater than AMP; other metabolites were apparently inactive. The potency of ATP was approximately 0.002 times that of histamine. In the forearm, cross tachyphylaxis was demonstrated between ATP and histamine weals; also the flare due to injected ATP spread beyond a band which was applied to prevent diffusion, indicating that the flare is neurogenic. Injections of ATP and high doses of ADP produced a sensation of persistent pain, unlike histamine which produced transient pain or itch on some occasions, and saline which was without effect. The possible involvement of histamine, mast cells and prostaglandins in the response was examined. The inhibitory actions of systemic pretreatment with diphenhydramine suggests that the erythema and wealing responses to ATP are at least partly due to ATP-evoked histamine release. Indomethacin, doxantrazole and cimetidine did not alter the ATP reaction.