Effects of Brefeldin A on disassembly of the Golgi body in MDCK cells subjected to a Ca2+ shift at low temperature.

When Madin-Darby canine kidney (MDCK) cells were grown in low-Ca2+ medium (LCM) the trans-Golgi cisternae, like those of cells maintained in high-Ca2+ medium (HCM), showed discrete localization of reaction product after thiamine pyrophosphatase (TPPase) staining. After exposure to Brefeldin A (BFA, 5 microg/ml) in LCM at 19 degrees C, the Golgi body dispersed and reaction product was distributed to the nuclear envelope and endoplasmic reticulum. The Golgi body reassembled in cells shifted back to HCM at 37 degrees C, with or without BFA, suggesting that low temperature and LCM exert synergistic effects in aiding dispersal of the Golgi apparatus in the presence of BFA. However, these results appear to be more directly correlated with the lack of defined cell polarity. Cells in LCM are unpolarized and both the centrosomes and the Golgi body are sub-nuclear in position, in contrast to their location in HCM where both organelles lie above the nucleus. The effects of BFA on the disassembly of the Golgi body therefore suggest that MDCK cells grown in LCM at low temperature cells are comparable to those non-polarized cell lines that are sensitive to BFA.