Prostaglandins may mediate chloride concentration gradient across domes formed by MDCK1 cells

The MDCK1 and LLC-PK1 cell lines have been used to characterize transepithelial transport in isolated culture. Both can be maintained in continuous culture and form domes that represent fluid actively transported from luminal to contraluminal surface. Fluid in domes from LLC-PK1 cells was isotonic with the culture medium and no Cl gradient between domes and medium was present. Fluid from domes formed by MDCK1 cells was also isotonic with respect to Na and K but there was a persistent Cl concentration gradient. To evaluate prostaglandin (PG) production by these cell lines, the culture medium was analyzed for PGE. LLC-PK1 cells released no measurable PGE; MDCK1 cells regularly released PGE both during basal conditions and after augmentation of PG synthesis by a high Ca concentration in the medium. Qualitatively similar results had previously been found with these cell lines when PG synthesis was augmented with addition of arachidonic acid or Ca ionophore A23187, and PGE or 6-keto-prostaglandin F1 alpha was measured in the medium. To evaluate whether PGs might be responsible for the Cl gradient across MDCK1 cells, indomethacin or meclofenamate was added. There was a marked decrease in the Cl gradient with either agent at 5 h. To evaluate the possibility that PGE2 or PGI2 plays a role in maintaining this Cl gradient, further studies were done in which indomethacin was added to the culture medium to block endogenous PG synthesis, and exogenous PGE2 or PGI2 was added. Although addition of PGE2 was without effect, addition of PGI2 to indomethacin-treated cells maintained the Cl gradient for at least 5 h.(ABSTRACT TRUNCATED AT 250 WORDS)