Phytoestrogen genistein inhibits carotid sinus baroreflex in anesthetized male rats / 生理学报

ABSTRACT

The purpose of this study was to determine the effect of phytoestrogen genistein (GST) on carotid sinus baroreflex in 30 anesthetized male rats by perfusing the isolated carotid sinus in vivo. The results obtained are as follows. (1) By perfusion with GST (50 micromol/L), the functional curve of baroreflex was shifted to the right and upward, with a peak slope (PS) decrease from 0.36+/-0.01 to 0.23+/-0.01 (P<0.001) and a reflex decrease (RD) in mean arterial pressure from 39.75+/-1.58 to 27.00+/-0.60 mmHg (P<0.001), while the threshold pressure (TP) and saturation pressure (SP) were significantly increased from 65.63+/-2.1 to 82.05+/-1.95 mmHg (P<0.001) and from 192.23+/-3.90 to 215.76+/-3.75 mmHg (P<0.001), respectively. Among the functional parameters of carotid baroreflex, the changes in RD, PS and TP were dose-dependent. (2) Pretreatment with Bay K 8644 (500 nmol/L), an agonist of calcium channels, could completely abolish the inhibitory effect of GST on carotid baroreflex. (3) Preperfusion with an inhibitor of NO synthase, L-NAME (100 micromol/L), did not affect the inhibitory effect of GST. It is proposed that the inhibitory action of GST on carotid baroreflex may be mediated by the inhibition of Ca(2+) channel of vascular smooth muscle, but not by NO release from endothelium.