title: Changes in the kinetics of muscle contraction in vitamin D-depleted rats.
abstract: Using an in situ rat soleus neuromuscular preparation, changes in the muscle contraction kinetics in response to vitamine D depletion were studied. For a single isometric contraction, the time-to-peak tension (Tp) and the time-for-recovery-half-way-to-resting tension (T1/2r) were recorded. For a 150 Hz, 300 msec tetanus, the T1/2r was determined. Animals raised on high-calcium, high-phosphate, vitamin D-depleted diets showed prolongation of all parameters. Repletion of vitamin D returned Tp and T1/2r values to normal. Neither dietary calcium deficiency nor thyroparathyroidectomy produced an prolongation of Tp or T1/2r values. Therefore, based upon the experimental data, it appears that vitamin D or one of its metabolites, independent of any effect on the serum calcium or serum phosphate concentration, is necessary for normal muscle relaxation.
mesh_terms: D000818:Animals; D002118:Calcium / Q000172:deficiency; D002136:Calcium, Dietary; D004195:Disease Models, Animal; D006801:Humans; D006996:Hypocalcemia / Q000503:physiopathology; D008297:Male; D009119:Muscle Contraction; D009132:Muscles / Q000378:metabolism / Q000503:physiopathology; D009135:Muscular Diseases / Q000503:physiopathology; D051381:Rats; D014808:Vitamin D Deficiency / Q000503:physiopathology*
chemical_list: D002136:Calcium, Dietary; D002118:Calcium