Effect of adenosine blockade on plasma renin activity and catecholamines.

We explored the hypothesis that chronic blockage of adenosine (Ado) receptors might augment the renin response to sodium restriction. In addition, an ancillary topic has been undertaken to test the hypothesis that endogenous Ado would restrain plasma norepinephrine (NE) and epinephrine (E) release. Male Sprague-Dawley rats (250 +/- 20 g) were fed with low sodium chow (Na+ 0.03%) and drank either distilled water or caffeine containing water (0.1%). Blood pressures were recorded in the presence of different concentrations of Ado. Plasma renin activity was measured at the beginning, 1 week and 6 weeks after the low sodium diet. An in situ autoperfused rat kidney model was used to examine whether renal function was influenced by chronic inhibition of Ado receptors. Furthermore, the effect of theophylline on cardiovascular actions of Ado in anaesthetized rats, and the effect of 1,3-dipropyl-8-(p-sulfophenyl)xanthine (DPSPX) on acute hydralazine induced NE and E release in conscious, unrestrained rats were also determined. Our data showed that the inhibitory effect of Ado on renin activity and blood pressure in salt restricted rats was attenuated by caffeine at the first week but not at six weeks after institution of the low sodium diet. Renal function in sodium restricted rats did not change after chronic caffeine consumption. Theophylline attenuated the dose-related inhibitory actions of Ado on blood pressure. Finally, DPSPX significantly increased plasma catecholamines, and these effects were much greater in rats treated with hydralazine. We conclude that the augmented renin response is not continued during chronic blockage of Ado receptors.(ABSTRACT TRUNCATED AT 250 WORDS)