Fig. 6. Role of DADLE-induced ERK1/2 phosphorylation in Bax translocation, Bcl-2 expression, survivin expression and cardiomyocyte apoptosis. (A) DADLE pretreatment induced a significant increase in ERK1/2 phosphorylation at 6 hours. This increase was prevented by either natrindole, or the ERK inhibitors, PD98059 and U0126, in cardiomyocytes cultured in DEPV conditions. (B) Translocation of Bax from cytosol into the mitochondria was assessed by comparing the cytosolic and mitochondrial Bax levels measured by western blot analysis at 6 hours. An increase in mitochondrial Bax with a concomitant decrease in cytosolic Bax indicates increased translocation of the protein into mitochondria. DEPV increased translocation of Bax from cytosol into the mitochondria. This translocation was prevented by DADLE. The effect of DADLE was abolished by natrindole, PD98059, or U0126. (C) DADLE-induced increase in Bcl-2 protein levels was prevented by either natrindole, PD98059, or U0126 at 6 hours. (D) Survivin level was significantly decreased in the cardiomyocytes cultured under DEPV conditions as assessed by western blot analysis at 6 hours. Values are mean ± s.d. (^*P<0.05, n=6 in each group). (E) The effect of DADLE in protecting the cardiomyocytes against apoptosis as assessed by TUNEL staining was prevented by PD98059 or U0126 (a, control; b, DEPV; c, DEPV+DADLE; d, DEPV+DADLE+PD98059). Values are mean ± s.d. (^*P<0.05, n=6 in each group). DEPV, serum and glucose deprivation; DADLE, [D-Ala2, D-Leu5]-enkephalin acetate salt; NAT, natrindole; PD98059, 2'-amino-3'-methoxyflavone; U0126, 1,4-diamino-2, 3-dicyano-1, 4-bis (2-aminophenylthio)-butadiene.