This study was designed to investigate the effects of phytoestrogen isoflavone on balloon catheter-induced hyperplasia of carotid artery.

Forty-eight female New Zealand rabbits were randomly divided into four groups: control (balloon-induced carotid artery injury only); ovariectomy control (ovariectomy and carotid artery injury), oestrogen (ovariectomy, carotid artery injury and nilestriol, 5mg/kg daily for 28 days), and isoflavone (ovariectomy, carotid artery injury and isoflavone 120mg/kg daily for 28 days). The arterial wall thickness was assessed by coloured ultrasonography, and the oestrogen-⍺ and oestrogen-β receptors in the abdominal aorta were measured by Western blotting.

The medial layer thickness in the isoflavone group was less than in the ovariectomy control group (0.28±0.03 vs. 0.35±0.04mm, p<0.01), and the intimal/medial layer (I/M) ratio is the isoflavone group was also less than in the ovariectomy control group (16.85±3.79 vs. 48.94±8.92, p<0.01). There was no statistically significant difference in the medial layer thickness or I/M ratio between the isoflavone and the oestrogen groups. The optical density of the oestrogen-⍺ receptors in the isoflavone group (0.317±0.002) was less than in the oestrogen (0.633±0.002) or ovariectomy control group (0.590±0.001, p<0.01). The optical density of the oestrogen-β receptors in the isoflavone group (1.350±0.002) and the ovariectomy control group (1.2033±0.002) was less than in the oestrogen group (1.7699±0.003, p<0.01).

Isoflavone therapy in the ovariectomised rabbit model attenuated balloon catheter-induced intimal and medial layer hyperplasia in the carotid arteries. Down-regulation of the oestrogen-⍺ receptors may be involved in the hyperplasia-preventative effect.