Abstract: Objective · To investigate the effect of 500 kHz pulsed ultrasound combined with SonoVue microbubbles on the vascular permeability of hind limbs in rats and the permeability dynamics for the duration. Methods · Eighty male Sprague Dawley rats were randomly divided into eight groups (n10), including control group, only microbubble group (MB group), and microbubble combined with ultrasound groups (MB+US group). And MB+US groups classified into time subgroups according to the interval the endpoint of ultrasound exposure to the injection of Evans blue (EB), included 2.5 min group, 5 min group, 10 min group, 20 min group, 30 min group and 60 min group. The change of vascular permeability was quantitively analyzeddetecting the content of EB after ultrasound irradiation. Meanwhile, four rats in each group were randomly selected. Two of them were performed hematoxylin-eosin (H-E) staining; and the rest of them underlied transmission electron microscope analysis. Results · The results of EB content detected muscle samples demonstrated that the exposure of ultrasound in conjunction with microbubbles could alter the vascular permeability of hind limbs of rats. The optimal time window for extravasation was within 30 min after ultrasound exposure. And the permeability could return to the normal status 60 min after ultrasound irradiation. There was no apparent damage on arteries and muscles in the slices with H-E staining. the observation of transmission electron microscope, the tight junctions between endothelial cells on the arterial wall were significantly widened in MB+US groups. Conclusion · The application of ultrasound with the frequency of 500 kHz combined with SonoVue microbubbles can reversibly change the vascular permeability of hind limbs in rats without obvious damage to the tissues.

Key words: ultrasound, microbubble, vascular permeability, rat, tight junction