Detrimental effects of short-term glucocorticoid use on the rat diaphragm

Background and Purpose. The purpose of this study was to determine the effe ct of short-term, high doses of glucocorticoids on both body and diaphragm weights as well as contractile characteristics of the rat diaphragm. Subjec ts. Adult, female Sprague-Dawley rats were divided into 2 groups: a control group (n=16) and a prednisolone group (n=16). Methods. The prednisolone gr oup received prednisolone at a dosage of 5 mg/kg, and the control group rec eived sham saline injections for 5 days. Animals were weighed prior to and after completion of the drug injection period. At the completion of the dru g injection period, the animals were sacrificed, and the diaphragm, soleus, and extensor digitorum longus muscles were removed and weighed. A small st rip of the costal diaphragm was connected to a force transducer, and the fo llowing contractile characteristics were measured: maximal specific isometr ic tetanic tension, peak isometric twitch specific tension, one-half relaxa tion time, and time to peak tension. Results. Both body and diaphragm weigh ts decreased by 15% in the prednisolone group as compared with the control group. Maximal specific isometric tetanic tension was reduced 13% in the pr ednisolone group as compared with the control group. There was no differenc e in any twitch contractile characteristics between the 2 groups. Conclusio n and Discussion. These data support the hypothesis that glucocorticoid tre atment over a 5-day period results in a decrease in specific tension as wel l as diaphragm and body weight. These results may have implications for the treatment of patients receiving high doses of glucocorticoids for acute me dical conditions.