Adenosine is known to produce biphasic effects in the renal tissues via adenosine receptors. However, the presence of more than one subtype of adenosine receptor on a type of kidney cell or tissue has not been conclusively demonstrated. To address this issue, we investigated the presence of A1 and A2 adenosine receptors in baby hamster kidney (BHK) cells by use of radioligand binding and the reverse transcription-polymerase chain reaction. Ligand binding studies with (3H)-DPCPX revealed a single class of binding site with a K(D) of 9.2 +/- 2.0 nM, a Bmax of 1.7 +/- 0.2 pmol/mg protein and a pharmacological profile characteristic of A1 adenosine receptor on the BHK cell membrane. As the presence of A2 adenosine receptors could not be conclusively determined by ligand binding studies, the more sensitive method of RT-PCR was employed. The presence of A1 and A2B adenosine receptors was detected by RT-PCR with specific primers and the subsequent sequencing of the resultant amplification product. The sequences obtained were 75-90% homologous to the respective adenosine receptor mRNA of rat, mouse and human.