Esau S A
Pulmonary Division, University of Virginia School of Medicine, Charlottesville 22908.
Am Rev Respir Dis. 1991 May;143(5 Pt 1):954-9. doi: 10.1164/ajrccm/143.5_Pt_1.954.
Hypoxic, hypercapnic acidosis (HHA) decreases tension and enhances fatigue in hamster diaphragm in vitro. We hypothesized that theophylline would decrease the harmful effect of HHA. Hamster diaphragm strips were studied in Krebs solution aerated with 21% O2 and 12% CO2. The force-frequency responses and the tension and relaxation of brief, submaximal contractions were studied. Mild fatigue was produced by a series of 45 submaximal contractions, after which recovery of force was followed for 15 min. Theophylline (0.55 mM) was added at the time of exposure to HHA (early theophylline) in half the strips and at the end of the fatigue run (late theophylline) in the others. In contrast to our hypothesis, early theophylline had a limited effect on force production in unfatigued HHA diaphragm strips and resulted in lower force production in the recovery period. Late theophylline improved force in the recovery period for low-frequency contractions. Thus the effect of theophylline in the setting of HHA depended on the time it was added and was beneficial only if added after the muscle stopped contracting.
低氧高碳酸血症酸中毒（HHA）会降低仓鼠离体膈肌的张力并增强其疲劳程度。我们推测氨茶碱会降低HHA的有害作用。在通有21% O₂和12% CO₂的 Krebs 溶液中对仓鼠膈肌条进行研究。研究了力-频率反应以及短暂次最大收缩的张力和舒张情况。通过一系列45次次最大收缩产生轻度疲劳，之后观察15分钟的力量恢复情况。在一半的膈肌条暴露于HHA时（早期氨茶碱组）加入氨茶碱（0.55 mM），另一半在疲劳试验结束时（晚期氨茶碱组）加入。与我们的推测相反，早期氨茶碱对未疲劳的HHA膈肌条的力量产生影响有限，并且在恢复期导致力量产生更低。晚期氨茶碱改善了低频收缩在恢复期的力量。因此，氨茶碱在HHA环境中的作用取决于添加时间，并且仅在肌肉停止收缩后添加才有益。
