Am. J. Respir. Crit. Care Med., Vol 153, No. 2, Feb 1996, 769-775.
Recovery of corticosteroid-induced changes in contractile properties and morphology of rat diaphragm
PN Dekhuijzen, G Gayan-Ramirez, A Bisschop, V de Bock, R Dom and M Decramer
Respiratory Muscle Research Unit, University Hospital, Katholieke Universiteit Leuven, Belgium.
Treatment with the fluorinated steroid triamcinolone (TR) induced type IIb
fiber atrophy and the contractile profile of a slow muscle in rat
diaphragm. In contrast, the nonfluorinated steroid prednisolone (PR) caused
myogenic changes without fiber atrophy, and increased fatigability. The aim
of the present study was to investigate the extent to which these changes
were reversed 2 mo after discontinuation of treatment. Adult rats were
randomly assigned to receive saline, PR 1.25 or 5 mg/kg, or TR 0.25, 0.5,
or 1 mg/kg, intramuscularly daily during 4 wk. Administration of TR
resulted in severe loss of body weight and dose-dependent mortality. During
recovery, body weight in the TR groups increased gradually, still remaining
reduced compared with the other groups. Two months after discontinuation of
treatment, diaphragm weight was increased in proportion to body weight.
Twitch characteristics, maximal tetanic force, force-frequency curve, and
fatigue resistance of isolated diaphragm bundles were similar in all
groups. Histologic examination of the diaphragm revealed no gross
abnormalities in the PR and TR groups. Mild but significant type IIb fiber
atrophy was still present in the diaphragm and gastrocnemius muscle of all
TR-treated animals. In conclusion, recovery of alterations in morphology of
respiratory and peripheral skeletal muscles induced by administration of TR
is prolonged.
