Effects of corticosteroid systemic administration on mechanical properties of rabbits diaphragm muscle

Abstract

High doses of systemic corticosteroids might promote metabolic myopathy. The aim of this study was to assess, by means of traction assays, the effects of myopathy induced by systemic corticosteroids on mechanical features of the diaphragm muscle of rabbits. Two groups of 15 female rabbits were studied: the experimental group (EG) received subcutaneous injections of methil-prednisolone (2 mg/Kg/day) during 21 days; the control group (CG) received subcutaneous saline. Traction assays were performed on proof fragments of left hemi-diaphragms. Histological analysis of diaphragm muscles was performed in three rabbits of each group. Mean percentages of variation between initial and final weight were -8.4±2.1% for the EG and 3.1±0.9% for the CG. No significant differences were found in mean values of tension and deformity at the maximum threshold, tension and deformity at the proportional threshold, or elasticity module between the groups. The histological analysis of EG diaphragms showed moderate irregularity in the diameter of myofibrils, with several myofagocitosis and hyaline necrosis fibers. In both groups, the diaphragm muscle showed the same elongation capacity and similar load tolerance. Hence the use of high doses of methilprednisolone does not provoke significant changes in the diaphragm mechanical properties, neither in plastic or elastic phases.