Rabbit model of acute femoral artery embolism

Forty-two New Zealand rabbits (male and female), weighing 1.8–2.8 kg, were acquired from the animal center of Xinjiang Medical University, Urumqi, China. The rabbits were provided with sufficient food and water and acclimated for 1 week before the experiments.

Heparin (1,000 U/kg) was bolus injected intravenously before thrombolytic therapy. The rabbits were anesthetized (pentobarbital, 30 mg/kg followed by 10 mg at 30- to 60-min intervals, via marginal ear vein injection). A 23-G catheter was inserted into the marginal ear vein for fluid maintenance. An incision was made in the femoral artery region. Femoral arteries were dissected 5 cm distal to the origin of the superficial branch, and the profound and superficial femoral arteries were ligated. A Doppler flow probe (Model TS420, Transonic System, Ithaca, NY, USA) was placed distally around the isolated segment to monitor blood flow. An occlusive suture was placed around the artery, and the distal clamps were loosened after 7 to 8 min. Occlusive thrombi were formed within 20 to 30 min, as expected, in all femoral arteries. Occlusive thrombi were detected by two-dimensional and color Doppler imaging. B-mode imaging showed the presence of low-echo-level thrombi over the local femoral artery, indicating that no blood flow, pulse signal, or microbubbles were present. The endpoint of thrombolytic therapy was set at 120 min after treatment³⁰.

Rabbits were then randomized to (n = 6/group): ultrasound alone (US); urokinase alone (UK); ultrasound plus non-targeted microbubbles (US + M); ultrasound plus RGDS-targeted microbubbles (US + R); RGDS-targeted microbubbles plus urokinase (R + UK); ultrasound, non-targeted microbubbles and urokinase (US + M + UK); and ultrasound, RGDS-targeted microbubbles and urokinase (US + R + UK) groups. The solution (3 ml) containing RGDS, microbubbles, and urokinase was administered to the rabbits as an intravenous bolus at 5 min duration, and 3 ml of the same solution solution were injected continuously over 20 min via the marginal ear vein. Then, the rabbits were subjected to contrast pulse sequencing to visualize the femoral artery. The MI was increased to 1.0 and applied at a frame rate of 3.1 MHz along the long axis plane. The MI was then turned back to 0.08, and images were captured again.

The animals were used according to the Guide for the Care and Use of Laboratory Animals. The experimental procedures were approved by the Ethics Committee of Xinjiang Medical University (No. 20090317001).