Tulobuterol patch maintains diaphragm muscle contractility for over twenty-four hours in a mouse model of sepsis

Tulobuterol, a sympathomimetic drug used as a transdermal patch, increases normal diaphragm muscle strength. Because diaphragm muscle weakness (i.e. decrease of contraction) is a feature of bronchial asthma and sepsis, we examined the in vitro and in vivo effects of tulobuterol on the contractility of diaphragm muscles prepared from mice treated with endotoxin. We measured contractile parameters of force-frequency curves and twitch kinetics using untreated or treated diaphragm muscles at 0 (E0) and 4 (E4) hours after E. coli endotoxin (20 mg/kg) administration. The force-frequency curve of E4 diaphragm muscle was decreased from that of E0 diaphragm muscle (p < 0.001). E4 diaphragm muscle was incubated in an organ buffer containing 10(-7) or 10(-5) M concentrations of tulobuterol for 1 h (in vitro). The force-frequency curves of both 10(-7) (p < 0.01) or 10(-5) M (p < 0.001) tulobuterol concentrations shifted significantly upward from those of no tulobuterol, indicating that tulobuterol can recover the diaphragm muscle contractility that was decreased by endotoxin. In the in vivo treatment, E0 and E4 diaphragm muscles were analyzed at 0, 12, and 24 h after transdermal tulobuterol treatment. The force-frequency curves of E0 and E4 diaphragm muscles at three time points were not significantly changed each other, indicating that tulobuterol patch restores the muscle contractility. Thus, diaphragm muscle contractility was maintained during 4 h of endotoxin administration with tulobuterol patch for over 24 h. We suggest that this treatment of bronchial asthma may protect against endotoxin contained in inhaled house dust.