ADENOSINE RECEPTOR GENE-EXPRESSION IN RAT-KIDNEY

Adenosine is an important modulator of renal function. Adenosine produced and released within the kidney is thought to participate in the metabolic regulation of glomerular filtration (tubuloglomerular feedback), as well as in regulating renal excretory function and renin secretion. The recent cloning of cDNAs encoding the A1 and A2a adenosine receptors from rat brain allows direct examination of potential sites of adenosine action within the rat kidney. Northern blot analysis of rat kidney poly(A)+ RNA revealed that A1 adenosine receptor mRNA was more abundant in kidney than the A2a adenosine receptor transcript. In situ hybridization With S-35-labeled cRNA probes was used to localize A1 and A2a adenosine receptor mRNAs within the kidney. A1 adenosine receptor mRNA was most abundant in the collecting ducts of the papilla and inner medulla. Collecting ducts in the outermost portion of the inner stripe of the outer medulla and cells of the juxtaglomerular apparatus also expressed A1 adenosine receptor mRNA. A2a adenosine receptor mRNA was localized to the renal papilla. The distribution of A1 and A2a adenosine receptor mRNAs within the rat kidney supports previously postulated roles for adenosine in the regulation of renal hemodynamics, excretory function, and renin secretion.