GENDER-SPECIFIC EFFECTS OF DEXAMETHASONE TREATMENT ON RAT DIAPHRAGM STRUCTURE AND FUNCTION

The effects of long-term dexamethasone treatment on diaphragm muscle w ere studied in female and male rats. Compared with pair-fed control an imals, dexamethasone treatment did not significantly affect estrous cy cling or peak serum estradiol levels; however, testosterone levels wer e significantly increased in females and decreased in males. Dexametha sone significantly reduced body and costal diaphragm weights, but to a lesser extent in females than in males. Reductions in diaphragm weigh t were proportional to reductions in body weight. In females and males , dexamethasone treatment significantly decreased diaphragm fiber (typ es I and II) cross-sectional area and the relative expression of myosi n heavy chain isoform 2B. With the exception of type I fiber atrophy, these changes occurred to a lesser extent in females. Dexamethasone di d not significantly affect specific forces. Dexamethasone significantl y increased twitch one-half relaxation time and fatigue resistance ind exes in males but not in females. In conclusion, the effects of long-t erm dexamethasone treatment were gender specific, with significantly f ewer effects in females, and changes in serum testosterone levels were associated with these findings.