2.1. Experimental design

Eight-week-old adult male Wistar rats with an average body weight of 240 ± 20 g (obtained from Pasteur Institute of Iran) were randomly allotted into five groups: controls cultured in the absence of VEGF (C) (Fig. 1), controls cultured in the presence of VEGF (C-V) (Fig. 2), controls treated with curcumin and then cultured in a medium lacking VEGF (C-TC) (Fig. 3), diabetics cultured in media supplemented with VEGF (D-V) (Fig. 4), and diabetics treated with curcumin and then cultured in media supplemented with VEGF (D-V-TC) (Fig. 5). Each group contained eight animals. All rats were provided standard laboratory rodent chow and water ad libitum. After 2 weeks, the experimental rats (groups D-V and D-V-TC) received a single intravenous injection of 60 mg/kg of body weight of STZ,¹⁷ whereas the control group received 60 mg/kg of vehicle. STZ was prepared fresh by dissolving in Na-citrate buffer (Sigma-Aldrich), pH = 4.5. In order to verify the diabetic condition, 96 h after the STZ injection, blood glucose levels of the experimental groups were measured using a portable glucose analyzer, Accu-check Blood Glucose Meter (Roche Diagnostics, Basel, Switzerland). Rats with blood glucose levels <15 mmol/L (270 mg/dl) received another injection of STZ. Following the second injection, animals with blood glucose levels higher than 15 mmol/L for 2 weeks were considered to be diabetic.

Optic microscopic view of endothelial cells of aortic ring in Group C.

Optic microscopic view of endothelial cells of aortic ring in Group C-V.

Optic microscopic view of endothelial cells of aortic ring in Group C-TC.

Optic microscopic view of endothelial cells of aortic ring in Group D-V.

Optic microscopic view of endothelial cells of aortic ring in Group D-V-TC.

Rats in the curcumin-treated groups (groups C-TC and D-V-TC) were given a solution of 100 mg/kg of curcumin per day (dissolved in 2 ml DMSO) by intragastric administration. Treatment with curcumin began 3 days prior to STZ administration and was continued for 8 weeks.