pH Heterogeneity of human and rabbit atherosclerotic plaques; a new insight into detection of vulnerable plaque

Background: Atherosclerotic plaques are heterogeneous with respect to inflammation, calcification, vascularity, oxygen, and temperature. We hypothesized that they also vary in pH and measured pH in living human carotid endarterectomized atherosclerotic plaques (CEA), Watanabe heritable hyperlipidemic (WHHL) rabbit aortas and human umbilical arteries (HUA). Methods and results: We measured pH of CEA of 48 patients, nine WHHL rabbit aortas and 11 HUA specimens (as controls) using a glass type microelectrode mounted on a micromanipulator in a 37 °C incubator. We also used single emission and also dual emission fluorescence ratio imaging microscopy employing pH-sensitive probes to confirm pH heterogeneity. Mean pH measured at 415 points of CEA was 7.55±0.32; at 275 points of WHHL rabbit aortas it was 7.40±0.43; and in 233 points of HUA it was 7.24±0.1. In CEA, pH of yellow (lipid-rich) areas was significantly lower than pH in calcified areas (7.15±0.01 vs. 7.73±0.01, P