Variability of functional characteristics of MDCK cells.

We measured several functional parameters of MDCK cells cultured as monolayers in order to more fully characterize their ion transport properties. Most of the present studies were completed with five groups (A-E) of MDCK cells studied from passage 62 to 78. Each group represents the same subline of MDCK cells after having been frozen, stored, and thawed at passage 62 or 64. The median transmonolayer resistances of the groups were 507, 149, 284, 72, and 126 omega X cm2. Addition of amphotericin B to the apical solution induced a oubain-sensitive transepithelial current. The apical membrane voltage and fractional resistance exhibited a wide range of values in two of the groups studied, with mean values of -32 mV and 0.68 in group B and -40 mV and 0.78 in group E. Neither apical nor basolateral membrane displayed significant Na+ conductance. K+ conductance was present in the basolateral but not in the apical membrane. Acidification or alkalinization of the apical solution was dependent on the conditions used to study the cells. The 4,4'-diisothyocyano-2,2'-disulfonic stilbene inhibited acidification (or induced alkalinization), whereas increasing ambient HCO-3 concentration induced alkalinization. The results of these studies indicate qualitatively similar behavior between five groups of MDCK cells but significant quantitative differences between the groups. Analysis of the variability of the measured parameters indicated that there were no differences as a function of passage number within a group. The factors responsible for functional differences between groups are not known but may be related to the cell storage process.