Effects of restraint and contrast ultrasound imaging on Hsp70 expression in cholesterol‐fed rabbit aorta (643.11)

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 stress the vascular tissue and increase levels of Hsp70, a cellular stress protein. Male New Zealand White rabbits (n=32) were fed a standard chow diet (n=4) or a 1% cholesterol, 10% fat and 0.11% magnesium diet (n=28). At 21 days, 24 rabbits on cholesterol diet were either exposed to US (3.2 MHz f/3 transducer, 2.1 MPa, Mechanical Index=1.17, 10 Hz pulse repetition frequency, 1.6 µs pulse duration, 2 min exposure duration at 4 sites) using the UCA Definity (1x concentration, 1 mL/min) or sham exposed using a saline control (n=12 per group). Four rabbits on cholesterol diet and the four on chow diet served as cage controls, and were not exposed to ultrasound or restrained for blood sample collection. Animals were euthanized 24 hours after exposure and aortas quickly isolated and snap‐frozen in liquid nitrogen. Aorta lysates from the area of US exposure were analyzed for Hsp70 protein level by Western blot. Blood plasma was analyzed for cholesterol and von Willebrand Factor (vWF), a marker of endothelial function. Plasma total cholesterol levels increased to an average of 705 mg/dL. Restraint (p<0.001 by ANOVA), but not US with UCA or cholesterol feeding, significantly increased Hsp70.Grant Funding Source: Supported by NIH R37EB002641 and the Beckman Institute Graduate Fellowship