Mesothelial cells are specialized epithelial cells, which line the pleural, pericardial, and peritoneal cavities. Accumulating
evidence suggests that the monolayer of mesothelial cells is permeable to electrolyte and fluid, and thereby
govern both fluid secretion and re-absorption in the serosal cavities. Disorders in these salt and fluid transport systems
may be fundamental in the pathogenesis of pleural effusion, pericardial effusion, and ascites. In this review, we discuss
the location, physiological function, and regulation of active transport (Na+-K+-ATPase) systems, cation and anion channels
(Na+, K+, Cl-, and Ca2+ channels), antiport (exchangers) systems, and symport (co-transporters) systems, and water
channels (aquaporins). These secretive and absorptive pathways across mesothelial monolayer cells for electrolytes and
fluid may provide pivotal therapeutical targets for novel clinical intervention in edematous diseases of serous cavities.