Effect of glucocorticoids on tumor necrosis factor induced suppression of protein synthesis in rat aortic smooth muscle: comparison with extensor digitorum longus.

Protein synthesis was measured in incubated aortic smooth muscle and fast-twitch extensor digitorum longus (EDL) in both sham operated and adrenalectomized (ADX) rats. The studies were performed on four groups: a) untreated controls; b) rats treated with tumor necrosis factor (TNF) @ 50 micrograms/kg. b.w.; c) rats treated with cortisone @ 100 mg/kg/day for 5 days; or d) rats treated with cortisone plus TNF. Both TNF and cortisone suppressed protein synthesis in the aortic smooth muscle and EDL in intact animals. TNF given together with cortisone, induced a significant additional decrease in protein synthesis in both muscle types as compared to cortisone-treated rats. The rate of protein synthesis in aortic smooth muscle from sham operated rats was control > TNF > cortisone > Cortisone+TNF; in the case of EDL, rate was control > cortisone > TNF > Cortisone+TNF. In ADX animals, TNF alone did not affect protein synthesis in both aortic smooth muscle and EDL. Though cortisone alone produced a significant inhibition of protein synthesis, there was no significant further decline in protein synthesis when cortisone was given together with TNF. These findings suggest that the inhibitory effect of TNF on muscle protein synthesis is mediated through glucocorticoids.