Dopamine regulates Na-K-ATPase in alveolar epithelial cells via MAPK-ERK-dependent mechanisms

Dopamine (DA) increases lung edema clearance by regulating vectorial Na+ tr ansport and Na-K-ATPase in the pulmonary epithelium. We studied the role of the mitogen-activated protein kinase (MAPK)-extracellular signal-regulated kinase (ERI() pathway in the DA regulation of Na-K-ATPase in alveolar epit helial cells (AEC). Incubation of AEC with DA resulted in a rapid stimulati on of ERK activity via dopaminergic type 2 receptors. Analysis of total RNA and protein showed a 1.5-fold increase in the Na-K-ATPase beta (1)-subunit mRNA levels and up to a fivefold increase in beta (1)-subunit protein abun dance after DA stimulation, which was blocked by the MAPK kinase (MEK) inhi bitors PD-98059 and U-0126. Also, the DA-ERK pathway stimulated the synthes is of a green fluorescent protein reporter gene driven by the beta (1)-subu nit promoter, which indicates that DA regulates the Na-K-ATPase beta (1)-su bunit at the transcriptional level. The DA-mediated increase in beta (1)-su bunit mRNA protein resulted in an increase in functional Na pumps in the ba solateral membranes of alveolar type II cells. These results suggest that t he MAPK-ERK pathway is an important mechanism in the regulation of Na-K-ATP ase by DA in the alveolar epithelium.