Modulation of liver cell membrane NHE-1, Na+-K+ ATPase, and GLUT-2 proteincontent after cold preservation and rewarming

Liver cell pH and volume regulation are perturbed by prolonged cold storage in University of Wisconsin solution and subsequent rewarming, but the mole cular basis of this effect remains unknown. We prepared membranes from hepa tocytes subjected to variable periods of cold preservation with or without subsequent rewarming and probed them by Western blotting with specific anti bodies against the Na+-H+ exchanger isoform NHE-1 and the Na+-K+ ATPase alp ha subunit. Results were compared with the content of GLUT-2, an abundant b asolateral protein. NHE-1 decreased significantly as cold preservation time s exceeded 10 h. Subsequent rewarming by short-term culture at 37 degrees C did not further reduce this parameter. On the other hand, expression of Na +-K+ ATPase remained stable during cold storage times lasting up to 48 h, w hereas rewarming resulted in a dramatic reduction in cells cold preserved b eyond 10 h. In contrast, the membrane content of GLUT-2 was unaffected by c old preservation with or without subsequent rewarming. The results indicate that cold storage and rewarming respectively and selectively modulate the expression of specific hepatocellular membrane transportproteins.