CLONING AND CHARACTERIZATION OF THE OPOSSUM KIDNEY-CELL D1 DOPAMINE-RECEPTOR - EXPRESSION OF IDENTICAL D1A AND D1B DOPAMINE-RECEPTOR MESSENGER-RNAS IN OPOSSUM KIDNEY AND BRAIN

Opossum kidney cells are an established epithelial cell line which is often studied as a physiological model system of renal proximal tubule function, and which has also been shown to possess dopamine receptors . To identify dopamine receptor subtypes present in renal tissue, as w ell as to explore the usefulness of opossum kidney cells for the study of Dl dopamine receptors and renal dopaminergic physiology, we have u ndertaken the cloning and characterization of the dopamine receptor ex pressed in this cell line. In the brains of rats and humans, two diffe rent subtypes of D1 dopamine receptors, D1A and D1B, have recently bee n characterized (1). The OK cell D1 receptor message is 4500 bp long a nd exhibits extensive homology with the rat and human D1A subtypes of dopamine receptors. Pharmacological experiments were performed on COS- 7 cell membranes transiently transfected with this cDNA. Binding prope rties were compared with those reported for OK cell membranes, and com parison experiments were performed in parallel with the human D1A expr essed transiently in the same system. Molecular techniques including N orthern blotting, in situ hybridization, and RNase protection analysis were used to study the expression pattern of the OK cell D1 receptor message. Expression of both D1A and D1B Subtypes was detected in both the opossum brain and the opossum kidney, however, the OK cell line ex presses exclusively the D1A receptor subtype.