Dinucleoside polyphosphates: a new class of cardiovascular hormones

Dinucleoside polyphosphates, a new group of hormones, are stored in cellula r granules and are released into the circulation after the cells have been stimulated. Dinucleoside polyphosphates then bind to specific receptors in other tissues and organs. Dinucleoside polyphosphates may either act as vas oconstrictors or as vasodilators. The type of action of the dinucleoside po lyphosphates in various vessels depends on the pattern of purinoceptor expr ession. In rabbit and guinea pig, cardiac preparations of dinucleoside poly phosphates showed a negative inotropic action. On the other hand, in human cardiac preparations a positive inotropic action of dinucleoside polyphosph ates was observed. A great number of enzymes degrading dinucleoside polypho sphates have been isolated from plasma as well as the extracellular surface of plasma membranes, further contributing to the complex picture of metabo lism and actions of dinucleoside polyphosphates as cardiovascular hormones. It may be speculated that dinucleoside polyphosphates, especially Ap(5)A, may play a role in the pathogenesis of hypertension. Ap(5)A has been shown to be the most potent agonist of the P-2X receptors mediating vasoconstrict ion. A P-2X receptor non-desensitized by Ap(5)A may underly the vasoconstri ction observed after continuous perfusion of the kidney with Ap(5)A. Potent ially, by further characterization of this receptor, an antagonist may be d eveloped which is capable of lowering blood pressure.