Discordant responses of mitogen-activated protein kinases to anoxia and freezing exposures in hatchling turtles

The role of two vertebrate mitogen-activated protein kinases (MAPKs) in med iating responses to in vivo anoxia or freezing exposures was examined in fo ur organs (liver, heart, kidney and brain) of hatchling red-cared turtles, Trachemys scripta elegans, which are naturally tolerant of these stresses. The extracellular signal-regulated kinases were not stress-activated except in brain of frozen turtles. The c-Jun NH2-terminal kinases (JNKs) were tra nsiently activated by anoxia exposure in all four organs (after 1 h in brai n or 5 h in other organs) but activity was suppressed during freezing excep t in brain which showed a transient activation of JNK after 1 h. Changes in the concentrations of the transcription factors, c-Fos and c-Myc, mere als o stress- and organ-specific. The patterns of MAPK activation in a stress-t olerant animal suggest the relative importance of these kinase pathways in cellular adaptation to oxygen deprivation or freezing and identify novel na tural activators of MAPKs in vivo. The specificity of the signaling pathway s is also emphasized here as the general whole-body stresses, anoxia and fr eezing, activated individual MAPKs in a tissue-, time-, and stress-dependen t manner.