EFFECT OF DIADENOSINE PHOSPHATES ON HUMAN UMBILICAL VESSELS - NOVEL PLATELET-DERIVED VASOCONSTRICTORS

The responses of human isolated umbilical artery to the novel platelet-derived mediators, diadenosine phosphates, P-1,P-5-di(adenosine-5')pentaphosphate (AP(5)A) and P-1,P-6- di(adenosine-5')hexaphosphate (AP(6)A) were studied in vitro. AP(5)A (1 nM-300 mu M; n = 7) and AP(6)A (1 nM-30 mu M; n = 5) produced transient concentration-dependent contractions. Responses to AP(5)A were unaffected by co-incubation with indomethacin (10 mu M; n = 4), N(G)monomethyl-L-arginine (L-NMMA; 300 mu M; n = 4) and theophylline (1 mu M; n = 5). These results demonstrate that diadenosine phosphates have constrictor effects on human blood vessels in vitro and are consistent with a role for these platelet-derived mediators in the regulation of blood vessel tone.