Figure 1.

Dopamine effects on alveolar epithelial cells and renal PCT cells. (A) Once dopamine is produced from its precursor L-dopa, it leaves to the luminal membrane (where it affects the sodium-dependent entry mechanisms located at the apical domain of the cells) and to the interstitium (where it regulates active sodium transport at the basolateral domain the cells). (B) Dopamine has two distinct effects: in the renal epithelium it inhibits Na⁺,K⁺-ATPase activity, whereas in the lung alveolar epithelium it stimulates its activity. Inhibition is brought about by a reduction in the amount of active units present at the plasma membrane, whereas stimulation is accomplished by recruiting new molecules to the plasma membrane from endosomal compartments.