ABSTRACT
Objective To investigate the effect of chronic electrical stimulus (CES) of low frequency and physiological frequency on diaphragmatic subtype of myosin heavy chain (MHC) and mechanical characteristic in rabbits with emphysema. Methods The rabbit model of emphysema was made by inhaling papain of ultrasonic atomization once a week for 3 weeks in 30 adult Japanese rabbits, 6 receiving 10 Hz chronic low-frequency electrical stimulation, 6 receiving 40 Hz, 6 receiving 10 Hz plus 40 Hz. Another 6 emphysema rabbits and 6 normal rabbits served as control. The twitch tension (Pt), titanic tension (Po), time to peak tension (TPT), half-relaxation time (1/2Rt), fatigue index (FI) and fatigue recovery index (FRI) were measured and SDS-polyacrylamide gel electrophoresis was used to observe the changes in subtype of MHC in control group, emphysema group, CES groups respectively. Results ①Following chronic electrical stimulus of 40 Hz, 10 Hz, and (10+40) Hz, the relative contents of MHC were increased in diaphragmatic muscle of rabbits with emphysema. The percentage of MHC-I was significantly increased in the 10 Hz group, while that of MHC-I and MHC-IIa were significantly increased in the (10+40) Hz group. ②Following chronic electrical stimulation using 40 Hz and (10+40)Hz, diaphragmatic muscle Pt and Po were significantly increased in rabbits with emphysema, TPT and 1/2Rt were significantly reduced, and FI and FRI were significantly decreased (P