[Effects of tramadol hydrochloride preconditioning on the activation of nuclear factor-ΚB induced by norepinephrine in cultured neonatal rat cardiomyocytes].

OBJECTIVE: To investigate the effects of tramadol hydrochloride preconditioning on activation of nuclear factor-ΚB (NF-ΚB) induced by norepinephrine (NE) in cultured neonatal rat cardiomyocytes. METHODS: 1 to 3-day old Sprague-Dawley (SD) rats were raised, and their cardiomyocytes were cultured for 4 to 5 days. Sixteen wells of cultured cardiomyocytes were randomly divided into four groups (n=4): blank control group, NE1 group in which the cells were incubated with 1×10(-6) mmol/L of NE, NE2 group in which cells were incubated with 1×10(-7) mmol/L of NE, and NE3 group in which cells were incubated with 1×10(-8) mmol/L of NE. Another 12 wells of cultured cardiomyocytes were randomly divided into three groups (n=4): blank control group, NE3 group in which cells were incubated with 1×10(-8) mmol/L of NE, tramadol plus NE group (T + NE group) in which cells were incubated with 1×10(-5) mmol/L of tramadol hydrochloride plus 1×10(-8) mmol/L of NE. Tramadol hydrochloride was added 30 minutes before the use of NE in T + NE group. After exposure to NE for 24 hours, the expression and activation of NF-ΚB in the cultured cardiomyocytes were determined by immunocytochemistry and flow cytometry (FCM). RESULTS: The results of immunocytochemistry showed that the expression of NF-ΚB (including average optical density and positive units) in NE3 group was significantly increased as compared with that in the blank control group (A average optical density: 0.30±0.03 vs. 0.12±0.04, t=7.200, P=0.008; positive units: 39±14 vs. 22±6, t=4.610, P=0.020). The results of FCM showed that the levels of cytoplasm NF-ΚB in cultured cardiomyocytes were decreased significantly in NE1 group, NE2 group and NE3 group compared with blank control group [(45.8±1.9)%, (38.3±1.8)%, (20.9±1.6)% vs. (54.6±0.6)%, all P<0.05], and the level in NE3 group was significantly lower than that in NE1 and NE2 groups (both P<0.05). The level of the cardiomyocytes cytoplasm NF-ΚB in T + NE group was higher than that in NE3 group [(57.8±0.4)% vs. (20.9±1.6)%, t=57.524, P=0.001]. CONCLUSIONS: Tramadol hydrochloride preconditioning can inhibit the activation of NF-ΚB induced by NE in cultured rat cardiomyocytes. It plays a protective role in ischemia myocardium at cell level.