Effects of palmatine on potassium and calcium currents in isolated rat hepatocytes

doi:10.3748/wjg.v9.i2.329

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Feb 15, 2003 (publication date) through Nov 23, 2024

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World Journal of Gastroenterology

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1007-9327

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Baishideng Publishing Group Inc, 7041 Koll Center Parkway, Suite 160, Pleasanton, CA 94566, USA

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World J Gastroenterol. Feb 15, 2003; 9(2): 329-333
Published online Feb 15, 2003. doi: 10.3748/wjg.v9.i2.329

Effects of palmatine on potassium and calcium currents in isolated rat hepatocytes

Fang Wang, Hong-Yi Zhou, Lan Cheng, Gang Zhao, Ji Zhou, Li-Ying Fu, Wei-Xing Yao

Fang Wang, Hong-Yi Zhou, Lan Cheng, Ji Zhou, Li-Ying Fu, Wei-Xing Yao, Department of Pharmacology, Tongji Medical College of Huazhong University of Science and Technology, Wuhan 430030, Hubei Province, China

Gang Zhao, Department of Pancreatic Surgery Center, Union Hospital, Tongji Medical College of Huazhong University of Science and Technology, Wuhan 430022, Hubei Province, China

Author contributions: All authors contributed equally to the work.

Correspondence to: Dr. Fang Wang, Department of Pharmacology, Tongji Medical College of Huazhong University of Science and Technology, Wuhan 430030, Hubei Province, China. wangfang0322@yahoo.com.cn

Telephone: +86-27-83692033

Received: September 14, 2002
Revised: October 4, 2002
Accepted: October 17, 2002
Published online: February 15, 2003

Abstract

AIM: To study the effects of palmatine, a known inhibitor on delayed rectifier potassium current and L-type calcium current (I_Ca,L) in guinea pig ventricular myocytes, on the potassium and calcium currents in isolated rat hepatocytes.

METHODS: Tight-seal whole-cell patch-clamp techniques were performed to investigate the effects of palmatine on the delayed outward potassium currents (I_K), inward rectifier potassium current (I_K1) and Ca²⁺ release-activated Ca²⁺ current (I_CRAC) in enzymatically isolated rat hepatocytes.

RESULTS: Palmatine 0.3-100 μM reduced I_K in a concentration-dependent manner with EC₅₀ of 41.62 ± 10.11 μM and nH, 0.48 ± 0.07 (n = 8). The effect of the drug was poorly reversible after washout. When the bath solution was changed to tetraethylammonium (TEA) 8 mM, I_K was inhibited. Palmatine 10 μM and 100 μM shifted the I-V curves of I_K downward, and the block of I_K was voltage-independent. Palmatine 0.3-100 μM also inhibited I_CRAC in a concentration-dependent manner. The fitting parameters were as follows: EC₅₀ = 51.19 ± 15.18 mM, and n_H = 0.46 ± 0.07 (n = 8). The peak value of I_CRAC in the I-V relationship was decreased by palmatine 10 μM and 100 μM. But the reverse potential of I_CRAC occurred at Voltage = 0 mV in all cells. Palmatine 0.3-100 μM failed to have any significant effect on either inward or outward components of I_K1 at any membrane potential examined.

CONCLUSION: The inhibitory effects on I_K and I_CRAC could be one of the mechanisms that palmatine exerts protective effect on hepatocytes.

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