Regulation of renal adenosine A1 receptors : effect of dietary sodium chloride

Abstract The influence of dietary NaCl on the regulation of renal adenosine A 1 receptors was investigated in the rat. Renal membranes from rats fed on a diet low (0.04%) in NaCl showed a 46% increase in B max for the binding of [ 3 H]-1,3-dipropyl-8-cyclopentylxanthine ([ 3 H]DPCPX), a selective adenosine A 1 receptor antagonist, compared to membranes from rats fed on a normal diet (0.4% NaCl). Conversely, a high NaCl diet (4.0%) resulted in a 37% decrease in B max . Levels of renal adenosine A 1 receptor mRNA were 65% lower in rats on a high salt diet. Autoradiographic studies showed that, for the inner medullary collecting ducts, a low NaCl diet resulted in a 30% increase in [ 3 H]DPCPX binding with a 39% decrease noted in rats maintained on a high salt diet. The results indicate that changes in adenosine A 1 receptor density may represent a novel mechanism whereby the kidneys adapt to changes in salt load.