title: Effects of different treatment regimens of methylprednisolone on rat diaphragm contractility, immunohistochemistry and biochemistry.
abstract: Systemic corticosteroid therapy may affect diaphragm structure and function. We postulated that functional, immunohistochemical and biochemical characteristics of rat diaphragm were less affected by alternate-day methylprednisolone (MP) administration, and more by repeated bursts of MP, in comparison to daily s.c MP. Sixty adult rats were randomized into four groups: saline s.c.; MP continuously (MP-C), 1 mg.kg-1 daily, MP alternate-day therapy (MP-A), 2 mg.kg-1 every other day; or MP in bursts (MP-B), MP 2 mg.kg-1 daily for 2 weeks, saline for 4 weeks, MP 2 mg.kg-1 daily for 2 weeks. The total treatment period was 8 weeks. Contractile properties of isolated diaphragm strips were measured. Antibodies reactive with type I, IIa, IIx and IIb myosin heavy chains were used for immunohistochemical analysis. Biochemical evaluation included markers of fast energy supply, glycogenolytic activity, beta-oxidation capacity and oxidative capacity. The force-frequency curve was depressed in all MP groups. Fibre type I, IIx and IIb cross-sectional area (CSA) decreased in all MP groups. Burst therapy decreased the contribution of type IIb fibres to total diaphragm muscle area. MP-A affected glycogenolytic activity less than MP-C. Burst MP therapy reduced creatine kinase (CK) activity and beta-oxidation capacity compared to MP-C. Oxidative capacity was increased in all MP groups. In conclusion, although the methylprednisolone treatment regimens affected diaphragm muscle morphology and bioenergetic enzyme activities in different ways, force generation decreased in all methylprednisolone treated groups to the same extent.
authors.affiliation: Dept of Pulmonary Diseases, University of Nijmegen, The Netherlands.
authors.forename: R H
authors.initials: RH
authors.lastname: van Balkom
authors.forename: H F
authors.initials: HF
authors.lastname: van der Heijden
authors.forename: H T
authors.initials: HT
authors.lastname: van Moerkerk
authors.forename: J H
authors.initials: JH
authors.lastname: Veerkamp
authors.forename: J A
authors.initials: JA
authors.lastname: Fransen
authors.forename: L A
authors.initials: LA
authors.lastname: Ginsel
authors.forename: H T
authors.initials: HT
authors.lastname: Folgering
authors.forename: C L
authors.initials: CL
authors.lastname: van Herwaarden
authors.forename: P N
authors.initials: PN
authors.lastname: Dekhuijzen
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000008:administration & dosage / Q000494:pharmacology*; D003402:Creatine Kinase / Q000378:metabolism*; D003964:Diaphragm / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D007150:Immunohistochemistry; D007271:Injections, Intradermal; D008297:Male; D008775:Methylprednisolone / Q000008:administration & dosage / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009132:Muscles / Q000201:enzymology; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000893:Anti-Inflammatory Agents; D003402:Creatine Kinase; D008775:Methylprednisolone