Change of transmembrane potential during delayed phase of noradrenaline preconditioning

AIM: To investigate the effect of noradrenaline (NA) on transmembrane potential during delayed preconditioning phase. METHODS: Primary culture myocardial cells of neonatal rat were randomly divided into three groups, namely, control (CON) group, hypoxia treatment (HT) group, and NA preconditioning (NAPC) group. CON group was cultured for 24 h without any drug interference, HT group was cultured for 24 h without any drug interference but then treated for 40 min with hypoxia, and NAPC group was exposed to NA (0.2 mg/L) for 10 min and then treated with hypoxia for 40 min after the 24-h culture. Fluorescence intensity (FI) of rhodamine-123-marked mitochondria was detected by flow cytometry. RESULTS: FI of the three groups was examined by analysis of variance (F=355.5, P<0.05). FIs of HT group and NAPC group were lower than that of CON group ［(6.24±0.13)%, (6.68±0.22)% vs. (8.32±0.19)%, P<0.05］. Transmembrane potentials of HT group and NAPC group were lower than that of CON group, indicating that the energy synthesis was defective. FI of NAPC group was higher than HT group and the transmembrane potential of NAPC group was higher than HT group, indicating that NA increased energy synthesis and improved cardiomyocyte metabolism. CONCLUSION: FI of NAPC group is higher than HT group, which indicates that NA improves the transmembrane potential.