Morphological evidence for the antiatherogenic effect of scoparone in hyperlipidaemic diabetic rabbits

Scoparone (6,7-dimethoxycoumarin), a coumarin isolated from a hypolipidaemic Chinese herb Artemisia scoparia, has vasodilator and antiproliferative activities and possesses free radical scavenging properties in vitro. The aim of the study was to investigate the morphological effects of scoparone in the antiatherogenic process in vivo by using hyperlipidaemic diabetic rabbits as an animal model.

Male New Zealand White rabbits were divided into three groups: control (normal), hyperlipidaemic diabetic, and scoparone treated hyperlipidaemic diabetic. The plasma concentration of total cholesterol and triglycerides were determined. The thickness of the tunica intima was measured on paraffin sections of the aortas stained with Movat's pentachrome. The aortic samples were also processed for scanning and transmission electron microscopy.

Neither the lipid profile in the plasma nor the structures of the aortic wall from the control group showed abnormalities. In contrast, the aortas from the hyperlipidaemic diabetic group showed prominent atherosclerotic plaques. Large numbers of monocytes were found adherent to the luminal surface and a markedly thickened intima filled with many lipid laden foam cells was clearly observed. By comparison, the scoparone treated group showed less advanced atherosclerosis with a lower plasma cholesterol. In the scoparone treated rabbits, the proportion of the aortic surface area covered with macroscopic plaques was 30%, and the thickness of the tunica intima 17%, of that of the non-scoparone treated hyperlipidaemic diabetic rabbits.

Scoparone has an antiatherogenic action in hyperlipidaemic diabetic rabbits.