ADENOSINE-A1-RECEPTOR MESSENGER-RNA IN MICRODISSECTED RAT NEPHRON SEGMENTS

Adenosine plays several roles in the kidney mediated by the specific r eceptors A(1), A(2), and possibly A(3). We studied the localization of adenosine A1( )receptor mRNA in rat nephron segments using reverse tr anscription and polymerase chain reaction (RT-PCR). The nephron segmen ts of male Sprague-Dawley rats (6 to 8 weeks old) were microdissected. Total RNA was prepared by the acid-guanidinium-phenol-chloroform meth od and used in the following RT-PCR assay. Because the PCR primers spa nned no intron, samples reacted in the absence of RT were used as cont rols for amplification of genomic DNA. The PCR products were size-frac tionated by electrophoresis, visualized with ethidium bromide staining , and confirmed by Southern blot analysis. PCR products were detected in all of the nephron segments examined. No signals were detected in s amples reacted in the absence of RT. Strong signals were detected in g lomeruli, medullary collecting duct, cortical thick ascending limb, an d medullary thick ascending limb, while weak signals were found in pro ximal convoluted and straight tubules. Previously, the presence of A(1 ) receptors has been demonstrated in glomeruli, collecting duct, and t hick ascending limb in the rat kidney by autoradiography and binding s tudies. In addition to these segments, we further detected A(1) recept or mRNA in proximal convoluted and straight tubules. Thus, A(1) recept or mRNA seems to be broadly expressed along the nephron.