Effects of Theophylline on Isolated Diaphragmatic Fibers
2015
An in vitro model of isolated diaphragmatic muscle fibers was developed to study the effects of theophylline on diaphragmatic contractility. The effects of theophylline on this model were compared for each dose with the effects of the drugs on a "classic" hemidiaphragmatic muscle preparation. Diaphragmatic strips obtained from 20 rats were placed into an open topped channel of a plexiglass tissue chamber and perfused with continuously flowing Krebs solution heated to 37° and bubbled with a 95% O2 and 5% CO2 gas mixture so as to maintain pH, Po2, Pco2 constant (7.4,100, and 35 mmHg, respectively). Isometric force generated in response to 1 Hz supramaximal electrical stimulation was measured with a highly sensitive photoelectric transducer. Graded doses of aminophylline (15 to 75 mg/L) were administered and their effect assessed on diaphragmatic peak twitch tension. On the single diaphragmatic muscle fibers preparation, theophylline produced a dose dependent increase in peak twitch tension, which, at a conc...
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