Formononetin: A Phytoestrogen and Isoflavone, Relaxes Guinea Pig Gallbladder Strips

Abstract

Background: Formononetin, a phytoestrogen and isoflavone, is present in red clover and several types of beans. It relaxes vascular smooth muscle and prostate smooth muscle. The purpose of this study was to determine if formononetin had an effect of gallbladder motility. Methods: An in vitro technique was used to determine which system mediated the relaxation. Formononetin (FMN) relaxed cholecystokinin octapeptide- (CCK) and KCl-induced tension in male guinea pig gallbladder strips in a concentration dependent manner. Both paired t -tests and analysis of variance were used for statistical analysis; differences between mean values of P < 0.05 were considered significant. Results: Adding FMN prior to CCK or KCl produced a significant decrease in the amount of tension (1.2 ± ­ 0.07 g vs. 0.81 ± 0.05 g CCK, P < 0.001; 0.84 ± 0.04 g vs. 0.74 ± 0.05 g KCl, P < 0.01). When the protein kinase C (PKC) inhibitors bisindolymaleimide IV and chelerythrine Cl - were used together, a significant (P < 0.01) reduction in the FMN-induced relaxation (78.1±4.5% vs. 69.7±3.4%) was observed. Genistein, a protein tyrosine kinase inhibitor, significantly (P < 0.01) decreased the amount of FMN-induced relaxation (72.2±6.5% vs. 59.3±6.5%). To determine if protein kinase A (PKA) mediated the FMN-induced relaxation, PKA inhibitor 14-22 amide myristolated (PKA-IM) was used. PKA-IM had no significant effect on the amount of FMN-induced relaxation. Neither the use of 2-aminoethoxydiphenyl borate (2-APB), a blocker of intracellular Ca 2+ release; KT5823, a blocker of protein kinase G; or L-NG-methyl-L-arginine acetate salt (L-NMMA), a nitric oxide synthase inhibitor, had a significant effect on the amount of FMN-induced relaxation. Conclusions: The FMN-induced relaxation of CCK- or KCl-induced tension was mediated by blocking extracellular Ca 2+ entry which then affected downstream events such as activation of PKC and protein tyrosine kinase. Cell Mol Med Res. 2017;000(000):000-000 doi: https://doi.org/10.14740/cmmr16e