EFFECTS OF ALFACALCIDOL ON THE CONTRACTILE PROPERTIES OF THE GASTROCNEMIUS MEDIALIS MUSCLE IN ADULT AND OLD RATS

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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. Supraphysiological 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.

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• EFFECTS OF ALFACALCIDOL ON THE CONTRACTILE PROPERTIES OF THE GASTROCNEMIUS MEDIALIS MUSCLE IN ADULT AND OLD RATS. (deposited 16 Jun 2011 12:36) [Currently Displayed]