Effects of vitamin D-3 on phosphate and calcium transport across and composition of skeletal muscle plasma cell membranes.
The effects of vitamin D-3 on calcium and phosphate transport in skeletal muscle plasma membranes were studied. Sarcolemma vesicles were isolated from vitamin D-deficient and vitamin D-treated (one week) chicks by sucrose density gradient centrifugation of a crude muscle plasma membrane fraction. Measurement of (Na+ + K+)-ATPase activity, cholesterol to phospholipid molar ratios and levels of intracellular marker enzymes showed a high degree of purification of the preparations. Administration of vitamin D-3 significantly increased active Ca2+ and phosphate uptake into the vesicles. The efflux of both ions from preloaded vesicles was only slightly altered by the sterol. Ca2+-ATPase activity was higher in sarcolemma from treated animals. This confirms that the effects of vitamin D-3 on calcium transport are related to the Ca2+ pump and not to the passive permeability properties of the membrane. No changes in the protein composition of vesicles from both experimental groups were observed. However, treatment with vitamin D-3 increased sphingomyelin and phosphatidylcholine concentrations. These changes in lipid structure may play a role in the effects of vitamin D-3 on transport characteristics of sarcolemma.
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002645:Chickens; D002762:Cholecalciferol / Q000494:pharmacology*; D002784:Cholesterol / Q000032:analysis; D007700:Kinetics; D008563:Membrane Lipids / Q000032:analysis; D009132:Muscles / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D010743:Phospholipids / Q000032:analysis; D012508:Sarcolemma / Q000032:analysis / Q000187:drug effects / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D014808:Vitamin D Deficiency / Q000378:metabolism*
D008563:Membrane Lipids; D010710:Phosphates; D010743:Phospholipids; D002762:Cholecalciferol; D002784:Cholesterol; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium