Expression of heat shock proteins in turtle and mammal hearts: relationship to anoxia tolerance

Heat shock proteins (HSPs) may play a cardioprotective role during hypoxia or ischemia. We hypothesized that cardiac tissue from hypoxia-tolerant anim als might have high levels of specific HSPs. We measured myocardial HSP60 a nd HSP72/73 in painted and softshell turtles during normoxia and anoxia (12 h) and after recovery (12 or 24 h). We also measured myocardial HSPs in no rmoxic rats and rabbits. During normoxia, hearts from the most highly anoxi a-tolerant species, the painted turtle, expressed the highest levels of HSP 60 (22.6 +/- 2.0 mg/g total protein) followed by softshells (11.5 +/- 0.8 m g/g), rabbits (6.8 +/- 0.9 mg/g), and rats (4.5 +/- 0.5 mg/g). HSP72/73 lev els, however, were not significantly different. HSP60 levels in hearts from both painted and softshell turtles did not deviate significantly from cont rol values after either 12 h of anoxia or 12 or 24 h of recovery. The patte rn of changes observed in HSP72/73 was quite different in the two turtle sp ecies. In painted turtles anoxia induced a significant increase in myocardi al HSP72/73 (from 2.8 +/- 0.1 mg/g normoxic to 3.9 +/- 0.2 mg/g anoxic, P < 0.05). By 12 h of recovery, HSP72/73 had returned to control levels (2.7 /- 0.1 mg/g) and remained there through 24 h (2.6 +/- 0.2 mg/g). In softshe ll turtles, HSP72/73 decreased significantly after 12 h of anoxia (from 2.4 +/- 0.4 mg/g normoxic to 1.3 +/- 0.2 mg/g anoxic, P < 0.05). HSP72/73 leve ls were still slightly below control after 12 h of recovery (2.1 +/- 0.1 mg /g) and then rose to significantly above control after 24 h of recovery (4. 1 +/- 0.7 mg/g, P < 0.05). We also conclude that anoxia-tolerant and anoxia -sensitive turtles exhibit different patterns of myocardial HSP changes dur ing anoxia and recovery. Whether these changes correlate with their relativ e degrees of anoxia tolerance remains to be determined.