Influence of dexamethasone on masseter muscle wet weight in growing rats

The objective of this study was to investigate the influence of corticosteroids on the masseter wet weight and changes after discontinuation of the administration by comparison with those of hind leg skeletal muscles. Thirty-five male Wister rats, 9 weeks old, were used for the experiment. As a corticosteroids, dexamethasone was administered in drinking water for 14 days in consentrations 0.5 and 3.0 μg/ml administration groups: LD (Low Dose group) and HD (High Dose group), respectively. A 21-day recovery period was set after the discontinuation. Recovery groups: LD-r and HD-r. Non-treated groups: CO (CO-b, CO, CO-r). After the experimental period, the superficial masseter and the rectus femoris and gastrocnemius were excised, and the wet weights were measured. The wet weights of each muscle were significantly lower in the LD and HD than in the CO (p < 0.05). More significant wet weight losses of hind leg were noted in the HD (p < 0.05). The wet weight reduction rates of the rectus femoris and gastrocnemius relative to those in the CO were 50 and 44% in the HD, but that of the masseter was only 25%. The reductions recovered to weights similar to those in the CO-r after the discontinuation in the LD-r, but the weights in the HD-r were significantly lower than those in the other 2 groups (p < 0.05). Dexamethasone reduced the wet weight of the superficial masseter in the growing rats, but the influence was smaller than that on the hind leg muscles, suggesting that the reduction can be recovered by discontinuation when the corticosteroids is not administered at high doses.