Effects of adenosine A1-agonist and -antagonist on urinary volume and Na excretion in IAP-treated and non-treated rats.

Effects of an adenosine A1-receptor agonist and antagonist were determined 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 filtration 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-dipropylxanthine) and 8-cyclopentyl-1,3-dipropylxanthine, adenosine A1-receptor antagonists, were not affected by pretreatment with IAP. These results suggest that endogenous adenosine may induce antidiuretic effects by accelerating the reabsorption of water and sodium at tubular sites via an IAP-insensitive mechanism, and that the diuretic effects of the adenosine A1-receptor antagonist may result from inhibiting this action of endogenous adenosine.