Response of epithelial (MDCK) cell junctions to calcium removal and osmotic stress is influenced by temperature

Intercellular junctions could be targets of injury during both hypothermic storage and cryopreservation. Monolayers of Madin-Darby canine kidney (MDCK) cells, an epithelial cell line, were grown on microporous membrane filters, and junction integrity was monitored by transepithelial electrical resistance (TER). At 37 degrees C, TER was 196 ohm . cm2 (SD 58, n = 59): this rose with falling temperature to 278 (SD 54) and 409 (SD 110) ohm . cm2, respectively, at 22 and 0 degrees C. This initial increase was accounted for solely by the change in conductivity of the bathing medium, which declined with falling temperature. Prolonged exposure to reduced temperature, however, did cause a gradual decline in TER. Removal of calcium at 22 degrees C caused a rapid fall in TER owing to dissociation of calcium-dependent components of the junctional complex. This was followed by a gradual increase in TER over several hours when calcium was restored to the bathing medium. At 0 degrees C, TER declined slowly regardless of the presence or absence of calcium, which suggested that reduced temperature stabilized junctions with respect to their calcium dependence, but that low temperature itself was causing dissociation of junctions. Hypertonic stress (597 mOsmol/kg) caused a reduction in TER both at 22 and 0 degrees C, which, unlike the reduction caused by calcium removal at 22 degrees C, was reversed relatively rapidly on return to isotonic conditions. Hypotonic stress (201 mOsmol/kg) increased TER at 0 degree C, but had no effect at 22 degrees C. The lack of response at the higher temperature might have been the result of a cell volume regulatory mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)