Relative biological effectiveness (RBE) of alpha radiation in cultured porcine aortic endothelial cells

Abstract

Purpose: Northern peoples can receive elevated radiation doses (1 – 10 mSv/y) from transfer of polonium-210 (210Po) through the lichen-caribou-human food chain. Ingested 210Po is primarily blood-borne and thus many of its short range alpha particles irradiate the endothelial cells lining the blood vessels. The relative biological effectiveness (RBE) of alpha particles vs. x-rays was examined in porcine aortic endothelial cells as a surrogate for understanding what might happen to human endothelial cells in northern populations consuming traditional foods.Materials and methods: Cultured porcine aortic endothelial cells were exposed to x-ray and 210Po alpha particle radiation. Alpha irradiation was applied to the cell cultures internally via the culture medium and externally, using thin-bottomed culture dishes. The results given here are based on the external irradiation method, which was found to be more reliable. Dose-response curves were compared for four lethal endpoints (cell viability, live cell fraction, release of lactate dehydrogenase [LDH] and clonogenic survival) to determine the relative biological effectiveness (RBE) of alpha radiation.Results: The alpha RBE for porcine cells varied from 1.6 – 21, depending on the endpoint: 21.2 ± 4.5 for cell viability, 12.9 ± 2.7 for decrease in live cell number, 5.3 ± 0.4 for LDH release to the medium but only 1.6 ± 0.1 for clonogenic survival. The low RBE of 1.6 was due to x-ray hypersensitivity of endothelial cells at low doses.