Effect of the flavonol quercetin on membrane conductances in rat colonic crypt cells.
Cermak R, Wolffram S, Kuhn G.
Institute of Animal Nutrition and Physiology, Christian-Albrechts-University of Kiel, Olshausenstr. 40, D-24098 Kiel, Germany. cermak@aninut.uni-kiel.de
The plant polyphenol quercetin was shown to induce Cl- secretion in rat colon. This study was performed to investigate the alterations of membrane conductances in isolated epithelial cells induced by quercetin. Whole-cell patch-clamp recordings were performed in isolated crypts from rat distal colon. In cells of the crypt basis, quercetin significantly hyperpolarized the membrane potential at concentrations > or =3 microM and increased the K+ conductance without visibly altering the Cl- conductance.
Thus, quercetin induces Cl- secretion merely by activation of K+ channels in the colon epithelium.
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Results of a tissue culture study suggest quercetin may be effective against excess scarring, or fibrosis. Fibrosis can cause problems in many areas of the body. Externally, it creates unsightly, raised keloid and hypertrophic scars after burns or other injuries. Internally, fibrosis causes life-threatening liver cirrhosis and kidney glomerulonephritis. In fibrosis, the cells that make scar tissue, or fibroblasts, are overactive. They multiply excessively, making too much collagen lattice, which contracts to form the three-dimensional scar. Currently, there is no satisfactory way to prevent or treat fibrosis.
To see if quercetin might help, Toan-Thang Phan, M.D., of the National University of Singapore, took tissue samples of fibroblasts from keloid and hypertrophic scars as well as from normal skin. He applied several types of natural compounds to the tissues and observed the results. Quercetin strongly inhibited the multiplication of keloid scar tissue cells but not the normal fibroblasts, in a dose-dependent manner. After the quercetin was removed from the environment, the keloid fibroblasts slowly resumed reproduction. Quercetin also normalized the collagen lattices so they did not contract. Other compounds, including curcumin from turmeric, also inhibited abnormal scarring, but quercetin was the most effective.
