DIADENOSINE PHOSPHATES AND THE PHYSIOLOGICAL CONTROL OF BLOOD-PRESSURE

OUR understanding of the regulation of vascular tone has been extended since the identification of vasoactive agents such as the atrial natr iuretic peptides1, endothelial-derived relaxing factor2 and endothelin 3. Unidentified vasopressive agents have been found in platelets4. Her e we isolate these vasopressors and identify them as diadenosine penta phosphate (AP5A) and diadenosine hexaphosphate (AP6A) by chromatograph y, mass spectrometry, ultraviolet spectroscopy and enzymatic cleavage. In the vasculature of isolated perfused rat kidney, both diadenosine phosphates were active at a concentration of 10(-9) M; in aortic rings , contractions were elicited at 10(-8) M. Intra-aortic injection in th e rat caused a prolonged increase in blood pressure. We conclude that AP5A and AP6A may play a part in local vasoregulation and possibly in the regulation of blood pressure.