Effects of phytoestrogen genistein on genioglossus function and oestrogen receptors expression in ovariectomized rats

Objective: This study was designed to investigate the effects of genistein on genioglossal muscle function and the expression of oestrogen receptors (ERB) in the ovariectomized rats. Design: Fifty female Sprague-Dawley rats were randomly divided into 5 groups: the control group (SHAM), the ovariectomized group (OVX), the ovariectomized rats receiving low genistein dosage (OVX+L), the moderate genistein dosage group (OVX+M) and the high genistein dosage group (OVX+H). Oestradiol level was detected by radioimmunity. The isometric twitch tension (P-t) and tetanic tension (P-0) of the GG muscle were measured in response to electrical field stimulation. The expression of ERs on the mRNA and protein levels was measured by real-time PCR and western blot respectively. Results: Ovariectomy decreased muscle fatigue resistance and the expression of different ERB significantly. Genistein treatment resulted in a dose-dependent protective effect on muscle fatigability and a parallel dose-responsive increase in the expression of oestrogen receptors mRNA and protein levels in genioglossus, with larger effects on oestrogen receptor beta vs. alpha. In contrast to the improvements in fatigability, there was no treatment effect on isometric twitch or tetanic tensions. Conclusion: The results indicated that genistein increased muscle fatigue resistance in addition to effects on receptors, and the up-regulation of receptors expression may be a possible mechanism by which genistein improved fatigue. (C) 2009 Elsevier Ltd. All rights reserved.