Inhibition by quercetin of thyroid hormone stimulation in vitro of human red blood cell Ca2+-ATPase activity |
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Authors: | F B Davis E Middleton P J Davis S D Blas |
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Institution: | 1. Endocrinology Division, Department of Medicine, State University of New York at Buffalo School of Medicine, the Erie County Medical Center, Buffalo, NY 14215 USA;2. Allergy Divisions, Department of Medicine, State University of New York at Buffalo School of Medicine, the Erie County Medical Center, Buffalo, NY 14215 USA;3. the Buffalo General Hospital USA |
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Abstract: | Human red blood cell membrane Ca2+-ATPase activity is stimulated in vitro by physiological concentrations of thyroid hormone. Quercetin, a flavonoid that inhibits several membrane-linked ATPases, suppressed thyroid hormone action on red cell Ca2+-ATPase activity and also interfered with binding of the hormone by red cell membranes. These effects of quercetin were dose-dependent over a range of concentrations (1-50 microM). In contrast, in the absence of thyroid hormone, quercetin at low concentrations stimulated Ca2+-ATPase activity and at 50 microM inhibited the enzyme. The effects of quercetin at low concentrations (1-10 microM), namely, stimulation of Ca2+-ATPase and inhibition of membrane-binding of thyroid hormone, mimic those of thyroid hormone and are consistent with the thyronine-like structure of quercetin. At high concentrations, quercetin is generally inhibitory of Ca2+-ATPase activity. Chalcone, fisetin, hesperetin and tangeretin are other flavonoids shown to reduce susceptibility of membrane Ca2+-ATPase to hormonal stimulation. |
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Keywords: | reprint requests to PJD |
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