Corrosion casts and scanning electron microscopy of choroidal vasculature in rats with inherited hypercholesterolemia

Purpose. The purpose of the present study is to determine the specific morphological changes in choroidal vasculature due to hypercholesterolemia. Methods. The choroidal vessels of rats with inherited hypercholesterolemia (RICO) were examined by the corrosion cast technique and electron microscopy. Results. In 18-month-old RICO rats, corrosion casts and scanning electron microscopy showed severe tortuosity, caliber irregularity and generalized dilatation of the large choroidal arteries and veins. The branch arterioles and draining venules were also tortuous and dilated. The ampullae of the vortex veins were wide, but no arteriovenous anastomoses, crossing defects or obstruction were seen. However, there were many venular collateral channels and venulovenular anastomoses. The choriocapillaries appeared normal. Transmission electron microscopy of the choroidal vessels showed hypertrophy of smooth muscle cells and irregular thickening of the basement membrane. The RPE and Bruch's membrane were intact. Conclusion. These findings indicate that the choroidal vascular changes are probably related to hypercholesterolemia. The results of the present study will be useful in the interpretation of the changes seen in hypertensive, diabetic and aged choroids.