Ischemia Induces Hsp70 Expression In Porcine Skeletal Muscle

2184 Ischemia causing a series of cellular changes is known to induce Heat-Shock-Protein70 (HSP70) in different tissues i.e. myocardium, brain, kidney and liver as shown in prior studies. It has been documented that HSP70 induction has protective effects against ischemic damage in these tissues. In a previous study on patients with peripheral arterial occlusive disease we observed an increased expression of HSP70 in involved muscles. This might suggest that ischemia in skeletal muscle induces HSP70 expression. Purpose: To investigate whether ischemia induces HSP70 expression in skeletal muscle. Methods: 21 3–4 months old swines were taken for the experiment. Complete ischemia was obtained by arterial ligation. Muscle biopsies were taken from the M. sternocleidomastoideus before ischemia (Normoperfusion, I0), after 2h of ischemia (I2) and after 4h of ischemia (I4). Total protein was extracted and after protein separation by SDS-PAGE HSP70 protein level was quantitated using Western Blot and densitometric analysis. Quantitative real-time RT-PCR was used to assess HSP70 mRNA level. Results: In comparison to I0 (34,9 ng for 25 ug protein loaded) HSP70 protein level showed a slight increase (N.S.) after 2h ischemia (37,5 ng) and an additional low increase after 4h ischemia (41,1 ng). However relative HSP70 mRNA concentration is clearly elevated in I2 (by 2,5 folds, p = 0,13) and there was a further significant upregulation in I4 compared to I0 (4,3 folds, p<0,05). Conclusion: The present study has demonstrated for the first time that ischemia can cause an upregulation of HSP70 expression in skeletal muscle. The lack of significant increase in HSP70 protein level may be attributed to reduced protein synthesis rate under ischemia. Therefore HSP70 induction might be considered as a stress indicator for the case of ischemia. Whether HSP70 upregulation can provide protection against ischemia in skeletal muscle as it has been shown in myocardium, requires further study.