DIADENOSINE PENTAPHOSPHATE AND HEXAPHOSPH ATE - NEW POTENT ENDOGENOUSVASOCONSTRICTORS

In the last decade our knowledge on the regulation of vascular tone wa s considerably extended, after several novel vasoactive substances had been identified, such as the atrial natriuretic peptides [5], EDRF [1 3] and endothelin [22]. In an earlier study, yet unidentified vasocons trictor substances had been described in platelets [18]. These substan ces have been identified as diadenosine pentaphosphate (AP(5)A) and di adenosine hexaphosphate (AP(6)A) by chromatography, mass spectrometry, UV-spectroscopy and enzymatic cleavage. In the vasculature of the iso lated perfused kidney both substances were vasoconstrictive in concent rations of greater than or equal to 10(-9) mol/l. In aortic rings cont ractions were elicited with concentrations of 10(-8) mol/l. Intra-aort ic injections in the rat caused a sustained increase in blood pressure . It is suggested that AP(5)A and AP(6)A play a role in the regulation of blood pressure.