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Effect of quercetin on colon contractility and L-type Ca2+ channels in colon smooth muscle of guinea-pig

HUANG Wei-Feng, OUYANG Shou, LI Shi-Ying, LIN Yan-Fei, OUYANG Hui, ZHANG Hui, LU Chun-Jing

Xiamen Medical Research Institute, Xiamen 361003, China； Department of Blood Transfusion, Maternal and Child Health Hospital of Xiamen, Xiamen 361003, China

Abstract

The aim of the present study was to investigate the effects of quercetin on colon contractility and voltage-dependent Ca2+ channels in the single smooth muscle cell isolated from the proximal colon of guinea-pig and to clarify whether its effect on L-type Ca2+ current (ICa,L) would be related to its myorelaxing properties. Colon smooth muscle strips were used to take contractile tension recordings. Smooth muscle cells were freshly isolated from the proximal colon of guinea-pig by means of papain treatment. IBa,L (barium instead of calcium as current carrier) was measured by using whole-cell patch-clamp techniques. The results showed that quercetin relaxed colon muscle strips in a concentration-dependent manner and antagonized the contractile effect of acetylcholine and neostigmine. Preincubation with indomethcin [cyclooxygenase (COX) inhibitor] and methylene blue [guanylate cyclase (GC) inhibitor] significantly attenuated the relaxing effect of quercetin, respectively. Quercetin increased IBa,L in a concentration- [EC50= (7.59±0.38) μmol/L] and voltage-dependent pattern, and shifted the maximum of the current-voltage curve by 10 mV in the depolarizing direction without modifying the threshold potential for Ca2+ influx. Quercetin shifted the steady-state inactivation curve toward more positive potentials by approximately 3.75 mV without affecting the slope of activation and inactivation curve. H-89 (PKA inhibitor) abolished quercetininduced IBa,L increase, while cAMP enhanced the quercetin-induced IBa,L increase. The patch-clamp results proved that quercetin increased IBa,L via PKA pathway. It is therefore suggested that the relaxing effect of quercetin attributes to the interaction of GC and COX stimulation, as well as the antagonism effect on acetylcholine, which hierarchically prevails over the increase in the Ca2+ influx to be expected from ICa,L stimulation.

Key words: quercetin; colon; L-type Ca2+ channels; guinea-pig

Received: 2009-09-17　　Accepted: 2009-11-12

Corresponding author: 欧阳守　　E-mail: xmmri@xmu.edu.cn

Citing This Article：

HUANG Wei-Feng, OUYANG Shou, LI Shi-Ying, LIN Yan-Fei, OUYANG Hui, ZHANG Hui, LU Chun-Jing. Effect of quercetin on colon contractility and L-type Ca2+ channels in colon smooth muscle of guinea-pig. Acta Physiol Sin 2009; 61 (6): 567-576 (in Chinese with English abstract).