EFFECTS OF ADENOSINE A(1)-AGONIST AND A(1)-ANTAGONIST ON URINARY VOLUME AND NA EXCRETION IN IAP-TREATED AND NON-TREATED RATS

Effects of an adenosine Al-receptor agonist and antagonist were determ ined in pertussis toxin (IAP)-treated and non-treated rats. (-)-N6-(2- phenylisopropyl) adenosine, an adenosine A1-agonist, reduced the urine volume and sodium excretion without decreasing the glomerular filtrat ion rate at 0.1 mg/kg (p.o.) in both IAP-treated and non-treated rats. Diuretic effects of KW-3902 (8-(noradamantan-3-yl)-1,3-dipropylxanthi ne) and 8-cyclopentyl-1,3-dipropylxanthine, adenosine A1-receptor anta gonists, were not affected by pretreatment with IAP. These results sug gest that endogenous adenosine may induce antidiuretic effects by acce lerating the reabsorption of water and sodium at tubular sites via an IAP-insensitive mechanism, and that the diuretic effects of the adenos ine A1-receptor antagonist may result from inhibiting this action of e ndogenous adenosine.