Gene expression of adenosine receptors along the nephron

Background. In view of the multiple effects of adenosine on kidney function, this study aimed to determine the expression of adenosine receptors (AR) along the rat and mouse nephron. Methods. For this purpose, we semiquantified mRNA abundance for adenosine A1-, A2A-, A2B-, and A3 receptors by RNAse protection and by reverse transcription-polymerase chain reaction (RT-PCR) in the kidney zones and in the different nephron segments of mice and rats. Results. We found very similar expression patterns for rat and mice. For the kidney zones A1- AR mRNA and A2A- AR mRNA abundance displayed a marked difference, with an increase from cortex to the inner medulla. This was not seen for A2B receptors, which showed in general a rather weak expression. Along the nephron, A1- AR was strongly expressed in the thin limbs of Henle and in the collecting duct system and to a lesser extent in the medullary thick ascending limb. A2A-AR mRNA was clearly detected in glomeruli but not in other nephron segments. A2B- AR mRNA was strongly expressed in the cortical thick ascending limb of Henle and in the distal convoluted tubule. A3-AR mRNA was not found in any nephron segment. Conclusion. Our data demonstrate a distinct mutual expression of the AR subtypes along the nephron. A1 receptors are expressed in medullary tubular structures, while A2B receptors are predominant in cortical tubular structures. A2A receptor expression in the kidney appears to be restricted to vascular cells.