Corticosteroid effects on isotonic contractile properties of rat diaphragm muscle

• Published in: Journal of applied physiology (1985) 1997-10, Vol.83 (4), p.1062-1067
• Main Authors: Van Balkom, Roland H. H, Zhan, Wen-Zhi, Prakash, Y. S, Dekhuijzen, P. N. Richard, Sieck, Gary C
• Format: Article
• Language: English
• Subjects: Adrenal Cortex Hormones - pharmacology; Animals; Biological and medical sciences; Diaphragm - cytology; Diaphragm - drug effects; Glucocorticoids - pharmacology; Hormones. Endocrine system; Isotonic Contraction - drug effects; Kinetics; Male; Medical sciences; Muscle Contraction - drug effects; Muscle Fibers, Skeletal - drug effects; Muscle Fibers, Skeletal - physiology; Muscle Fibers, Skeletal - ultrastructure; Myosin Heavy Chains - metabolism; Pharmacology. Drug treatments; Physical Endurance - drug effects; Physical Endurance - physiology; Prednisolone - pharmacology; Rats; Rats, Sprague-Dawley; Space life sciences
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/jappl.1997.83.4.1062

Roland H. H. Van Balkom 1 , Wen-Zhi Zhan 2 , Y. S. Prakash 2 , P. N. Richard Dekhuijzen 1 , and Gary C. Sieck 2 , 3 1  Department of Pulmonary Diseases, University Hospital Nijmegen, Nijmegen 6500 HB, The Netherlands; and Departments of 2  Anesthesiology, and 3  Physiology and Biophysics, Mayo Clinic and Foundation, Rochester, Minnesota 55905 Received 16 December 1996; accepted in final form 8 May 1997. Van Balkom, Roland H. H., Wen-Zhi Zhan, Y. S. Prakash, P. N. Richard Dekhuijzen, and Gary C. Sieck. Corticosteroid effects on isotonic contractile properties of rat diaphragm muscle. J. Appl. Physiol. 83(4): 1062-1067, 1997. The effects of corticosteroids (CS) on diaphragm muscle (Dia m ) fiber morphology and contractile properties were evaluated in three groups of rats: controls (Ctl), surgical sham and weight-matched controls (Sham), and CS-treated (6 mg · kg 1 · day 1 prednisolone at 2.5 ml/h for 3 wk). In the CS-treated Dia m , there was a selective atrophy of type IIx and IIb fibers, compared with a generalized atrophy of all fibers in the Sham group. Maximum isometric force was reduced by 20% in the CS group compared with both Ctl and Sham. Maximum shortening velocity in the CS Dia m was slowed by ~20% compared with Ctl and Sham. Peak power output of the CS Dia m was only 60% of Ctl and 70% of Sham. Endurance to repeated isotonic contractions improved in the CS-treated Dia m compared with Ctl. We conclude that the atrophy of type IIx and IIb fibers in the Dia m can only partially account for the CS-induced changes in isotonic contractile properties. Other factors such as reduced myofibrillar density or altered cross-bridge cycling kinetics are also likely to contribute to the effects of CS treatment. prednisolone; skeletal muscle; fiber type; shortening velocity; fatigue; endurance 0161-7567/97 $5.00 Copyright © 1997 the American Physiological Society