title: Changes in adenine nucleotide, SOD and MDA contents and mitochondria ulteractructure during diaphragm fatigue in dogs induced by diaphragm pacing.
abstract: OBJECTIVE: To explore the possible mechanisms for the occurrence of diaphragm fatigue induced by diaphragm pacing. METHODS: The phrenic nerve of 8 dogs were exposed and subjected to stimulation with electric pulses emitted by a diaphragm pacemaker to induce diaphragm fatigue models, and the contents of ATP, ADP, AMP and AXP in the diaphragm muscles before and after diaphragm pacing were determined by high-performance liquid chromatography (HPLC). The contents of SOD and MDA were also measured and the morphological alteration of the mitochondria observed with transmission electron microscope. RESULTS: The contents of ATP, ADP, AXP and SOD were found significantly lower but MDA was higher during fatigue than those in normal conditions, while AMP content manifested no obvious change. Some mitochondria in the diaphragm muscles swelled and in a few cases, vacuolar degeneration was observed. CONCLUSIONS: The exhaustion and synthesis disturbance of ATP may explain the generation of diaphragm fatigue, and the reduction of dynamophore and ultrastructural injuries of the cells induced by oxygen free radicals may also contribute to this result.
authors.affiliation: Department of Cardiothoracic Surgery, Nanfang Hospital, First Military Medical University, Guangzhou 510515, China.
authors.forename: Wen-Feng
authors.initials: WF
authors.lastname: Cao
authors.forename: Gang
authors.initials: G
authors.lastname: Chen
authors.forename: Rui-Jun
authors.initials: RJ
authors.lastname: Cai