title: Effects of alfacalcidol on the contractile properties of the gastrocnemius medialis muscle in adult and old rats.
abstract: Vitamin D deficiency is associated with muscle weakness. It is unknown, however, how supra-physiological levels of vitamin D affect skeletal muscle. To investigate the effects of increased serum vitamin D (1,25 (OH)₂D₃ or 1,25D) levels on the contractile properties of the medial gastrocnemius muscle, adult and old female Fischer₃₄₄ x Brown Norway F1 rats were orally treated with vehicle or the vitamin D analogue alfacalcidol for 1 or 6 weeks. Alfacalcidol treatment resulted in elevated 1,25D serum levels. This was accompanied by hypercalcaemia and a reduction in body mass, the latter largely attributable to a reduced food intake. However, kidney function, as reflected by normal creatinine serum levels, as well as heart mass were unaffected. The 17% reduction in maximal isometric force and power was explicable by a similar loss of muscle mass. The force-frequency relationship of the 6-week-treated old rats was shifted to the left, but neither the shape of the force-velocity relationship nor the fatigability of the muscle were altered. Supra-physiological doses of vitamin D were accompanied by significant reductions in body and muscle mass, but not by an improvement in muscle functioning. Weight loss was largely due to a reduced food intake, while the left shift in the force-frequency relation may be due to increased 1,25D levels.
authors: Institute for Biomedical Research into Human Movement and Health, Manchester Metropolitan University, Manchester, United Kingdom.
authors: J
authors: J
authors: Testerink
authors: H
authors: H
authors: Degens
authors: J
authors: J
authors: Rittweger
authors: A
authors: A
authors: Shiraishi
authors: R T
authors: RT
authors: Jaspers
authors: A
authors: A
authors: de Haan
mesh_terms: D000367:Age Factors; D000818:Animals; D015992:Body Mass Index; D002117:Calcitriol / Q000031:analogs & derivatives / Q000097:blood; D003404:Creatinine / Q000097:blood; D004326:Drinking / Q000187:drug effects; D004435:Eating / Q000187:drug effects; D005221:Fatigue / Q000097:blood / Q000503:physiopathology; D005260:Female; D006887:Hydroxycholecalciferols / Q000494:pharmacology*; D006934:Hypercalcemia / Q000139:chemically induced; D007537:Isometric Contraction / Q000187:drug effects*; D018908:Muscle Weakness / Q000097:blood / Q000503:physiopathology; D018482:Muscle, Skeletal / Q000187:drug effects*; D051381:Rats; D011914:Rats, Inbred BN; D011916:Rats, Inbred F344; D014808:Vitamin D Deficiency / Q000097:blood / Q000503:physiopathology
chemical_list: D006887:Hydroxycholecalciferols; D003404:Creatinine; D002117:Calcitriol; C008088:alfacalcidol