The present study was aimed at evaluating the role of D1- and D2-like receptors and investigating whether inhibition of Na+ transepithelial flux by dopamine is primarily dependent on inhibition of the apical Na+/H+ exchanger, inhibition of the basolateral Na+-K+-ATPase, or both. The data presented here show that opossum kidney cells are endowed with D1- and D2-like receptors, the activation of the former, but not the latter, accompanied by stimulation of adenylyl cyclase (EC50 = 220 ± 2 nM), marked intracellular acidification (IC50 = 58 ± 2 nM), and attenuation of amphotericin B-induced decreases in short-circuit current (28.6 ± 4.5% reduction) without affecting intracellular pH recovery after CO2 removal. These results agree with the view that dopamine, through the activation of D1- but not D2-like receptors, inhibits both the Na+/H+ exchanger (0.001933 ± 0.000121 vs. 0.000887 ± 0.000073 pH unit/s) and Na+-K+-ATPase without interfering with the Na+-independent HCO[Formula: see text] transporter. It is concluded that dopamine, through the action of D1-like receptors, inhibits both the Na+/H+ exchanger and Na+-K+-ATPase, but its marked acidifying effects result from inhibition of the Na+/H+exchanger only, without interfering with the Na+-independent HCO[Formula: see text] transporter and Na+-K+-ATPase.
Stimulation of inorganic phosphate transport by insulin-like growth factor I and vanadate in opossum kidney cells is mediated by distinct protein tyrosine phosphorylation processes.