Expression of dopamine D(1A) receptor gene in proximal tubule of rat kidneys

The existence of dopamine receptor subtypes outside the central nervous system has been suggested by pharmacological and biochemical techniques. Whether the renal dopamine receptors are distinct from those cloned from the brain remains to be determined. Indeed, the expression of any of these receptor genes in the kidney has not been demonstrated definitively. In this study, we amplified D(1A) receptor cDNA from microdissected proximal convoluted tubules of the rat kidney by reverse transcription-polymerase chain reaction; primers were based on the sequence of rat D(1A) cDNA cloned from the brain and corresponded to the third cytoplasmic loop of the receptor. Specificity of the amplified products was verified by restriction analysis, Southern blots, and sequencing. Furthermore, solution hybridization indicated the presence of a single ribonuclease-protected RNA species corresponding to the D(1A) receptor mRNA in proximal tubules. These studies report for the first time the presence of D(1A) receptor message in the kidney.