Contrast ultrasound imaging does not affect Hsp70 expression in cholesterol‐fed rabbit aorta

Abstract

Diagnostic ultrasound imaging (US) is enhanced by the use of circulating microbubble contrast agents (UCAs), but the interactions between US, UCAs, and vascular tissue are not well understood. We hypothesized that US with UCA would represent a stress to the vascular tissue at the site of exposure and increase levels of Hsp70, a cellular stress protein. Male New Zealand White rabbits (n=24) were fed a diet containing 1% cholesterol, 10% fat and 0.11% magnesium. At 21 days, rabbits were either exposed to US (2.1 MPa) using the UCA Definity or sham exposed using a saline control (n=12 per group). Blood plasma was analyzed for cholesterol and von Willebrand Factor (vWF), a marker of endothelial function. Animals were euthanized 24 hours after exposure and a section of the abdominal aorta was quickly isolated and snap‐frozen in liquid nitrogen. Aorta lysates from the specific area of US exposure were analyzed for Hsp70 protein expression by Western blot. Plasma total cholesterol levels increased to an average of 705 mg/dL. Hsp70 was expressed in aortas of both groups. No significant differences were observed between the two groups in Hsp70 expression or plasma vWF levels. Elevation of plasma cholesterol is a substantial stress to the vasculature, and the stress protein Hsp70 was expressed in vascular tissue. No additional vascular stress was observed as a result of US imaging. [Supported by NIH R37EB002641]