Modulation of the low affinity Ca2+-binding sites of skeletal muscle and blood platelets Ca2+-ATPase by nordihydroguaiaretic acid |
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Authors: | Barata Hosana Cardoso Cristiana M Wolosker Herman de Meis Leopoldo |
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Institution: | (1) Instituto de Ciências Biomédicas, Departamento de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, Brazil |
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Abstract: | The antioxidant nordihydroguaiaretic acid (NDGA) inhibited the different sarco/endoplasmic reticulum Ca2+-ATPase isoforms found in skeletal muscle and blood platelets. For the sarcoplasmic reticulum, but not for the blood platelets Ca2+-ATPase, the concentration of NDGA needed for half-maximal inhibition was found to vary depending on the substrate used and its concentration in the assay medium. The phosphorylation of the sarcoplasmic reticulum Ca2+-ATPase by ATP and by Pi were both inhibited by NDGA. In leaky vesicles, measurements of the ATP Pi exchange showed that NDGA increases the affinity for Ca2+ of the E2 conformation of the enzyme, which has low affinity for Ca2+. The effects of NDGA on the Ca2+-ATPase were not reverted by the reducing agent dithiothreitol nor by the lipid-soluble antioxidant butylated hydroxytoluene. |
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Keywords: | Ca2+-ATPase nordihydroguaiaretic acid Ca2+ affinity |
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