ABSTRACT
Objective Role of melanocortin receptor 4 (MCAR) in excitatory amino acid release from rat astrocytes in spinal cord. Methods Astrocytes were isolated from the spinal cord of newborn pathogen-free Wistar rats ( 1-3 days after birth) and cultured in serum-free Neurobasal/B27 liquid culture medium. After 4 passages the primary cultured astrocytes were randomly divided into 3 groups (6 wells each): group Ⅰ control (group C); group Ⅱ the astrocytes were exposed to TNF-α 10 μg/L (group T) and group Ⅲ the astrocytes were exposed to TNF-α 10 μg/L and HS014 (selective MC4R antagonist) 1 μmol/L (group TH). The astrocytes were incubated at 37 ℃ for 3 h. The supernatant was collected for determination of glutamic acid (Glu) and aspartic acid (Asp)concentrations by HPLC-MS/MS. Results TNF-α significantly increased Glu and Asp release from astrocytes in group T as compared with group C. The Glu and Asp concentrations were significantly lower in group TH than in group T. Conclusion MG4R is involved in the excitatory amino acid release from astrocytes in the spinal cord.
ABSTRACT
Objective To investigate the effect of nicorandil pretreatment on myocardial mitochondria in a rabbit model of myocardial ischemia-reperfusion (I/R). Methods Tirty-two healthy male New Zealand white rabbits weighing 2.0-2.5 kg aged 4 months were randomly allocated into 4 groups ( n = 8 each): Ⅰ group sham operation (group S); Ⅱ group I/R; Ⅲ group nicorandil pretreatment (group N) and Ⅳ group nicorandil + 5 hydroxydecanoic acid (group N + 5-HD). Myocardial I/R was induced by 30 min occlusion of left circumflex coronary artery followed by 120 min reperfusion. In group N and N + 5-HD a bolus of nicorandil 100 μg/kg was given iv at 10 min before myocardial ischemia followed by continuous infusion at 10 μg· kg-1 · min-1 until the beginning of myocardial ischemia. In group Ⅳ a bolus of 5-HD 5 mg/kg was injected iv at 20 min before myocardial ischemia.The animals were sacrificed at the end of 120 min reperfusion. The mitochondrial membrane potential was measured by flow cytometry using JC-1 fluorescence probe as indicator. Bcl-2, Bax and cytochrome c protein expression was determined by immuno-histochemistry. Myocardial ultrastructure was examined with transmission electron microscope. Results Red fluovescence intensity indicating normal live cells was significantly higher, the green fluorescence intensity indicating apoptotic cells was lower and red/green fluorescence intensity ratio was higher; the Bcl-2/Bax ratio was significantly higher and cytochrome c protein expression lower in group N than in group I/R.5-HD administration negated the protective effect of nicorandil pretreatment against myocardial I/R injury. Conclusion Nicorandil stabilizes mitochondrial membrane potential, decreases cytochrome c protein releasing, and suppresses mitochondrial apoptotic signal transduction by opening the mito-KATP channels.