Cold-induced microtubule disruption and relocalization of membrane proteins in kidney epithelial cells

Cold preservation of kidneys is commonly used in human transplantation and in vitro studies. However, although disruption of the cytoskeleton by cold has been demonstrated in cultured cells, the effect of cold treatment on intact kidney is poorly understood. In this study, specific antibodies were used to examine the effect of hypothermia on the cytoskeletal network and the trafficking of some membrane proteins in the urinary tubule. Rat kidneys were cut into thin slices (approximately 0.5 mm) that were divided into several groups: (1) some were immediately fixed in paraformaldehyde, sodium periodate, and lysine (PLP); (2) some were stored at 4 degrees C for 15 min or 4 h before being fixed in cold PLP; or (3) after 4 h cold treatment, some slices were rewarmed to 37 degrees C for 15, 30, and 60 min in a physiologic solution, pH 7.4, and were then fixed in warm PLP. Immunofluorescence staining revealed an almost complete disruption of the microtubule network in proximal tubules after 15 min cold treatment, whereas microtubules in other segments were affected after 4 h. A partial recovery of the microtubule network was observed after 60 min rewarming. In contrast, actin filaments seemed to be resistant to cold treatment. gp330, aquaporin-2, H+ ATPase, and the AE1 anion exchanger were all relocated into numerous vesicles that were distributed throughout the cytoplasm after hypothermia followed by rewarming, whereas Na-K-ATPase retained its basolateral localization. The vasopressin-stimulated insertion of aquaporin-2 water channels into the apical membrane was inhibited during the initial rewarming period after cold exposure. Thus, cold preservation of tissues might impair, at least transiently, the polarized membrane expression and function of some transport proteins in renal epithelial cells.