OBJECTIVES: To investigate the potential for plant derived estrogens (phytoestrogens) genistein, phloretin, biochanin A and zearalanone to relax rabbit coronary arteries in vitro and to determine the mechanism(s) of such relaxation. BACKGROUND: Epidemiological data suggests a reduction in the incidence of coronary heart disease in humans who have a high intake of phytoestrogens. METHODS: Isolated rabbit coronary artery rings were suspended in individual organ baths, precontracted with potassium chloride (30 mM), and the relaxing effects and mechanisms of relaxation to genistein, phloretin, biochanin A and zearalanone were determined by measurement of isometric tension. RESULTS: Genistein, phloretin and biochanin A induced significant gender-independent relaxation in rings with and without endothelium. Inhibition of nitric oxide and prostaglandin synthesis with L-NAME and indomethacin had no effect on genistein-induced relaxation. Relaxation was unaffected by the specific estrogen receptor antagonist ICI 182,780, the ATP-sensitive potassium channel inhibitor glibenclamide and the potassium channel inhibitor, barium chloride. Calcium concentration-dependent contraction curves in high potassium depolarization medium were significantly shifted to the right and downward after incubation with genistein and zearalanone. An inhibitory effect of genistein (2 microM) on L-type calcium current in guinea-pig ventricular myocytes confirmed a calcium antagonist relaxing mechanism of action. In healthy volunteers, plasma genistein levels of approximately 2 microM are achieved after ingestion of a commercially available soy protein drink (Supro) containing 37 mg genistein. CONCLUSIONS: This study demonstrates that phytoestrogens induce endothelium-independent relaxation of coronary arteries; the mechanism involves calcium antagonism. These mechanisms may contribute to the potential long-term cardiovascular protective effect of these substances.
OBJECTIVES: To investigate the potential for plant derived estrogens (phytoestrogens) genistein, phloretin, biochanin A and zearalanone to relax rabbit coronary arteries in vitro and to determine the mechanism(s) of such relaxation. BACKGROUND: Epidemiological data suggests a reduction in the incidence of coronary heart disease in humans who have a high intake of phytoestrogens. METHODS: Isolated rabbit coronary artery rings were suspended in individual organ baths, precontracted with potassium chloride (30 mM), and the relaxing effects and mechanisms of relaxation to genistein, phloretin, biochanin A and zearalanone were determined by measurement of isometric tension. RESULTS:Genistein, phloretin and biochanin A induced significant gender-independent relaxation in rings with and without endothelium. Inhibition of nitric oxide and prostaglandin synthesis with L-NAME and indomethacin had no effect on genistein-induced relaxation. Relaxation was unaffected by the specific estrogen receptor antagonist ICI 182,780, the ATP-sensitive potassium channel inhibitor glibenclamide and the potassium channel inhibitor, barium chloride. Calcium concentration-dependent contraction curves in high potassium depolarization medium were significantly shifted to the right and downward after incubation with genistein and zearalanone. An inhibitory effect of genistein (2 microM) on L-type calcium current in guinea-pig ventricular myocytes confirmed a calcium antagonist relaxing mechanism of action. In healthy volunteers, plasma genistein levels of approximately 2 microM are achieved after ingestion of a commercially available soy protein drink (Supro) containing 37 mg genistein. CONCLUSIONS: This study demonstrates that phytoestrogens induce endothelium-independent relaxation of coronary arteries; the mechanism involves calcium antagonism. These mechanisms may contribute to the potential long-term cardiovascular protective effect of these substances.
Authors: Lee-Jane W Lu; Nai-Wei Chen; Fatima Nayeem; V-M Sadagopa Ramanujam; Yong-Fang Kuo; Donald G Brunder; Manubai Nagamani; Karl E Anderson Journal: Clin Nutr Date: 2017-11-11 Impact factor: 7.324
Authors: William W H Ng; Wendy Keung; Yan Chun Xu; Kwok F J Ng; George P H Leung; Paul M Vanhoutte; Patrick C Choy; Ricky Y K Man Journal: Mol Cell Biochem Date: 2007-12-30 Impact factor: 3.396