Effects of Acute Steroid Administration on Ventilatory and Peripheral Muscles in Rats

Occasional case reports have shown that acute myopathy may occur in patients treated with massive doses of corticosteroids. The mechanism of this myopathy is poorly understood. Therefore, 60 male rats were randomly assigned to receive daily injection of saline (C), methylprednisolone (M), or triamcinolone (T) 80 mg/kg/d for 5 d. Nutritional intake, measured daily in 15 animals, showed a significant reduction of food intake in the steroid-treated groups (-50 and -79% in M and T, respectively). This was associated with a similar loss in body weight. In the 45 remaining animals, diaphragm contractility and histopathologic features of several muscles were studied. Weights of respiratory and peripheral muscles were similarly decreased after steroid treatment. Maximal twitches of the diaphragm were lower in the C group (653 +/- 174 g/cm(2)) than in the M group (837 +/- 171 g/cm(2); p < 0.05) and the T group (765 +/- 145 g/cm(2), NS). Half-relaxation time was prolonged in both steroid groups, and time to peak te...