Hypophosphatemia is responsible for skeletal muscle weakness of vitamin D deficiency.
A deficiency of vitamin D results in muscle weakness as well as rickets in children and osteomalacia in the adult. To study the basis for this weakness, severe vitamin D deficiency was produced in rats as revealed by a low level or absence of 25-hydroxyvitamin D(3) in the serum. Vitamin D deficiency was achieved by feeding purified diets to weanlings for 16 weeks. Muscle force, peak contraction (P), time-to-half contraction (T(1/2)), time-to-peak contraction (T(P)), and time-to-half recovery (T(1/2r)) were measured. A significant reduction in muscle force was found when vitamin D deficiency was accompanied by hypophosphatemia. Within 2 days of correcting the hypophosphatemia, muscle strength was normalized. When serum calcium and serum phosphorus were maintained in the normal range in vitamin D-deficient rats, muscle weakness did not develop. Further, hypocalcemia together with vitamin D deficiency did not produce muscle weakness. These results strongly suggest that muscle weakness noted in rachitic patients is the result of the hypophosphatemia of vitamin D deficiency.
Department of Biochemistry, University of Wisconsin-Madison, 53706-1544, United States.
Laurie
L
Schubert
Hector F
HF
DeLuca
D000328:Adult; D000818:Animals; D002648:Child; D004195:Disease Models, Animal; D006801:Humans; D017674:Hypophosphatemia / Q000150:complications* / Q000503:physiopathology; D008297:Male; D009119:Muscle Contraction; D018656:Muscle Fibers, Fast-Twitch / Q000502:physiology; D018657:Muscle Fibers, Slow-Twitch / Q000502:physiology; D053580:Muscle Strength; D018908:Muscle Weakness / Q000209:etiology* / Q000503:physiopathology; D018482:Muscle, Skeletal / Q000503:physiopathology; D051381:Rats; D017208:Rats, Wistar; D012279:Rickets / Q000209:etiology / Q000503:physiopathology; D014808:Vitamin D Deficiency / Q000150:complications* / Q000503:physiopathology