Mitogen-activated protein kinases and anoxia tolerance in turtles

The response of two vertebrate mitogen-activated protein kinase (MAPK) fami ly members, the extracellular signal-regulated kinases (ERKs) and c-Jun NH2 -terminal kinases (JNKs), to anoxia exposure in vivo was examined in organs (liver, heart, kidney, brain, spleen) of the anoxia-tolerant adult turtle, Trachemys scripta elegans. ERKs activities rose during anoxia only in sple en (a 2.8-fold increase). JNK activity showed a significant increase only i n liver (4-fold increase) after 5 hr of anoxic submergence but declined the reafter. Levels of the transcription factor c-Fos were strongly suppressed in liver, heart, and kidney of anoxia-exposed turtles, whereas levels incre ased 2-fold in anoxic brain. The effect of anoxia on c-Myc was organ-specif ic and variable with 2- and 1.5-fold increases in protein expression in kid ney and brain, respectively, and a 60% decrease in anoxic spleen. These res ults for an anoxia-tolerant animal suggest the potential importance of the MAPKs and of the immediate-early genes (c-fos, c-myc) in mediating adaptive responses to oxygen deprivation. J. Exp. Zool. 287:477-484, 2000. (C) 2000 Wiley-Liss, Inc.