The conductance of cultured epithelial cell monolayers: oxidants, adenosine triphosphate, and phorbol dibutyrate.

Oxidants are one class of inflammatory molecules that may contribute to an increase in epithelial permeability to water and solutes that commonly occurs during acute inflammation. We and others have observed that oxidants reversibly alter the paracellular conductance of Madin Darby canine kidney epithelial (MDCK) cell monolayers. The mechanism by which oxidants reversibly alter MDCK monolayer conductance is not yet fully understood. Some investigators have suggested that oxidants might alter MDCK monolayer paracellular conductance by depleting adenosine triphosphate (ATP) in the cells. When we exposed MDCK cells to doses of oxidants that increased monolayer paracellular conductance in earlier studies, ATP was depleted within 10 min. However, when ATP was depleted to similar levels with an inhibitor of glycolytic ATP production, 2-deoxy-D-glucose (DOG), monolayer paracellular conductance was not increased. Severe ATP depletion with DOG and the mitochondrial metabolic inhibitor, antimycin A (AA), had very limited, ATP-independent effects on paracellular conductance. As an alternative explanation for the effects of oxidants on MDCK monolayer paracellular conductance, we had reported that oxidants increased production of inositol phosphates and diglycerides in MDCK cells. Synthetic diglyceride and phorbol dibutyrate (PDBU) increased MDCK monolayer conductance to ions and mannitol in earlier studies. When MDCK cell ATP was depleted with DOG (to the level caused by oxidants), the increase in conductance following PDBU was not different from that observed in control cells. More severe ATP depletion, with DOG and AA, prevented the increase in conductance following PDBU.(ABSTRACT TRUNCATED AT 250 WORDS)