Emodin increases Ca(2+) influx through L-type Ca(2+) channel in guinea pig gallbladder smooth muscle.
Emodin is known to be used in the treatment of cholesterol stones and cholecystitis. This study sought to investigate the effects of emodin on the contraction of gallbladder smooth muscle (GBSM), intracellular Ca(2+) concentration and L-type calcium current in GBSM cells. Gallbladder muscle strips were obtained from adult guinea pigs and the resting tension was recorded. Gallbladder smooth muscle cells were isolated by enzymatic digestion. Cells were loaded with fluo-3/AM and [Ca(2+)](i) was determined by a laser confocal microscope. Calcium current was recorded by the whole-cell patch clamp method. Emodin increased the resting tension of GBSM strips in a dose-dependent manner. Emodin elevated [Ca(2+)](i) in GBSM cells, and this effect was attenuated by pretreatment with nifedipine. In addition, Emodin increased L-type calcium current at concentrations of 1 to 30 microM (at +10 mV, 10 microM, 45.1+/-5.2% compared to control, EC(50) =3.11 microM). In the presence of protein kinase C (PKC) inhibitor, Staurosporine, emodin did not significantly affect the calcium current. However, phorbol 12, 13-dibutyrate mimicked emodin in enhancement of the calcium current. These results suggest that emodin promotes gallbladder contraction by increasing Ca(2+) influx through L-type calcium channel via PKC pathway.
Wu
Zhi-Xuan
ZX
Department of Gastroenterology, Renmin Hospital, Wuhan University, Wuhan, China.
Yu
Bao-Ping
BP
Xia
Hong
H
Xu
Long
L
D000818:Animals; D002120:Calcium Channel Agonists / Q000494:pharmacology*; D020746:Calcium Channels, L-Type / Q000187:drug effects* / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004642:Emodin / Q000494:pharmacology*; D005260:Female; D005704:Gallbladder / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D019311:Staurosporine / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors
D002120:Calcium Channel Agonists; D020746:Calcium Channels, L-Type; D047428:Protein Kinase Inhibitors; D011493:Protein Kinase C; D019311:Staurosporine; D004642:Emodin; D013755:Tetradecanoylphorbol Acetate