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Short-term vs long-term dexamethasone treatment: effects on rat diaphragm structure and function
D J Prezant1, M L Karwa, B Richner
1Department of Medicine, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY 10467, USA.
Lung
|June 9, 1998
Summary
Dexamethasone treatment in rats reduced body weight and diaphragm muscle mass. Longer treatment (10 weeks) caused greater changes in myosin heavy chain isoforms and fiber atrophy, but increased fatigue resistance.
Area of Science:
- Physiology
- Pharmacology
- Muscle Biology
Background:
- Dexamethasone is a potent corticosteroid with known effects on skeletal muscle.
- The impact of dexamethasone treatment duration on diaphragm muscle characteristics is not fully understood.
Purpose of the Study:
- To investigate the effects of different dexamethasone treatment durations on diaphragm myosin heavy chain isoforms, fiber types, and contractile properties in male rats.
- To determine if the observed effects are dependent on treatment duration.
Main Methods:
- Male rats received dexamethasone for 2.5 or 10 weeks.
- Body weight, diaphragm weight, myosin heavy chain (MHC) isoform expression, fiber type distribution, and contractile characteristics were assessed.
- Comparisons were made against ad libitum-fed and pair-fed control groups.
Main Results:
- Dexamethasone significantly decreased body weight and costal diaphragm weight.
- Relative expression of MHC-2B isoform decreased, with a greater effect after 10 weeks.
- Type I and type II fiber atrophy occurred, more pronounced in type II fibers after 10 weeks.
- Costal diaphragm-specific forces remained unaffected.
- Fatigue resistance increased significantly, especially after long-term treatment.
Conclusions:
- Dexamethasone-induced changes in MHC isoform phenotype, fiber atrophy, and fatigue resistance are duration-dependent.
- Longer dexamethasone exposure (10 weeks) leads to more pronounced effects on diaphragm muscle characteristics.