Dopamine acutely decreases type 3 Na +/H + exchanger activity in renal OK cells through the activation of protein kinases A and C signalling cascades

Abstract

Dopamine D 1-mediated inhibition of Na +,K +-ATPase activity in opossum kidney (OK) cells involves the sequential activation of the adenylyl cyclase–protein kinase A (PKA) and the phospholipase C–protein kinase C (PKC) pathways [Am. J. Physiol. Renal Physiol. 282 (2002) F1084.]. The present study evaluated the signalling cascades involved in dopamine-mediated inhibition of Na +/H + exchanger isoform 3 (NHE3) in OK cells. The transport kinetics displayed a simple Michaelis–Menten relationship for extracellular Na + of 25±6 mM. Dopamine and the dopamine D 1-like receptor agonist SKF 38393 ((±)-1-phenyl-2,3,4,5-tetrahydro-(1 H)-3-benzazepine-7,8-diol) inhibited NHE3 activity in a concentration-dependent manner; the dopamine D 2-like receptor agonist quinerolane was devoid of effect. The SKF 38393-mediated inhibition of NHE3 was prevented either by the dopamine D 1-like receptor antagonist SKF 83566 ((±)-7-Bromo-8-8-hydroxy-3 methyl-1-phenyl-2,3,4,5-tetrahydro-1 H-3-benzazepine; 1 μM), overnight treatment with cholera toxin (500 ng/ml), the PKA antagonist H-89 ( N-(2-[ p-bromocinnamylamino]ethyl)-5 isoquinolinesulfonamide hydrochloride; 10 μM), the PKC antagonist chelerythrine (1 μM), or the phospholipase C inhibitor U-73,122 (1-(6-[(17β]-3-methoxyestra-1,3,5[10]-trien-17-yl) amino] hexyl)-1 H-pyrrole-2,5-dione; 3 μM). In addition, dibutyril cAMP (dB-cAMP; 500 μM) was found to increase phospholipase C activity, both in membranes and in cytosol from OK cells; in contrast, phorbol-12,13-dibutyrate (PDB) (1 μM) did not have a significant effect on phospholipase C activity. Pre-treatment of OK cells with the anti-G sα antibody, but not the anti-G q/11α antibody, blunted the inhibitory effect of SKF 38393 on NHE3 activity. It is concluded that dopamine D 1-mediated inhibition of NHE3 in renal OK cells involves both adenylyl cyclase–PKA and the phospholipase C–PKC pathways, a mechanism similar to that described for Na +,K +-ATPase.