Effects of long-term injection of steroid hormone on soluble protein in rat muscles and organellae.

Steroid hormone (dexamethasone, 0.1 mg/kg/day) was injected into Wistar strain rats, and its effect on the weight of organellae and skeletal muscles was studied. Steroid was injected for 20, 30 and 40 weeks, and a de-steroid group was obtained by interrupting the steroid injections for three weeks. The body weight of the injected rats decreased by 40 to 60% from that of the control, even when food intake per body weight was increased by more than 20%. The weight of organellae (heart, liver and adrenal glands) apparently decreased. Nevertheless, the weight per body weight tended to recover to the control level in the de-steroid group. Muscle atrophy of the proximal muscles, the rectus femoris and the semimembranosus muscles was observed in the steroid group. Remarkable atrophy appeared in the semimembranosus muscle, named type II fiber, with 40% to 60% of control at the 30th and 40th weeks and the recovery rate of this weight was determined in only 80% in the de-steroid group. A decrease of the 40,000 to 60,000 MW polypeptides of serum and muscle soluble protein fraction was shown in the 40-week group. These results suggested that acceleration of glycolysis, glyconeogenesis and protein catabolism were induced after long-term steroid injection.