MUSCLE STRENGTH AND FATIGUE IN GLUCOCORTICOID-TREATED RATS

Glucocorticoids, which are prescribed as anti-inflammatory agents, can cause secondary osteoporosis and skeletal muscle atrophy. We examined the effects of glucocorticoids on the muscle strength and muscle fatigability in rats. Six-month-old female Wistar rats were randomized into two groups：1) the control group, which received daily injections of normal saline and 2) the predonisolone (PSL) group, which received PSL 10 mg/kg daily. After a 4-week treatment period, the maximum contractile strength (to measure muscle strength) and strength decrement index (SDI) (to measure muscle fatigue) were evaluated by contractile properties using three different stimulations：1) 20-Hz tetanic, 2) 40-Hz tetanic, and 3) 100-Hz cyclical. The cross sectional area (CSA) was measured at the left tibialis anterior (TA) muscle. Contractile muscle strength by 40-Hz tetanic stimulation, but not the other stimulations, significantly decreased in the PSL groups compared to the control group; decreases occurred in a time-dependent manner (p