Single dose whole-body irradiation causes acute and reversible increases in large artery stiffness in rats

Exposure to high energy radiation causes cardiovascular injury. It has been demonstrated that whole-body gamma irradiation impairs the endothelial-dependent vasomotor function. Such impairment may cause increased arterial stiffness, as can be shown by increased pulse wave velocity (PWV). The current study aims to determine the effects of whole-body high-dose high-energy X-ray on aortic PWV. Male Sprague-Dawley rats (14 weeks old) were exposed to a single high-dose of high-energy X-ray (source: LINAC, 6 MV) at either 0 (control) or 5 Gy (irradiated). Between 0 to 24 hours, 24 to 48 hours and 3 weeks following irradiation, rats were anaesthetized (1.3 g/kg, urethane) and beat-to-beat PWV (m/s) and mean arterial blood pressure (MAP) measured invasively using two 1.3 F high fidelity pressure sensors (SciSense Inc, Canada) positioned in the descending thoracic aorta via the right femoral and left carotid arteries. Arterial pressure was increased and decreased over the range of 60–150 mmHg with intravenous infusion of phenylephrine and sodium nitroprusside respectively. Across the blood pressure range, mean aortic PWV in the irradiated rats measured within 24 hours postirradiation was 5.080.15 m/s, a 14% increase compared to the control group (4.440.11 m/s, n12; P0.05). No significant difference was observed between the PWV in the irradiated group measured in the 24–48 hour period post-irradiation and the control group (4.140.10 m/s, n4; P0.14). Similarly, no difference was found in the arterial stiffness of control and irradiated rats 3 weeks after radiation (control 4.370.14 m/s, irradiated 4.530.13 m/s, n12; P0.41). Whole-body exposure to a single dose of high-energy X-ray increased aortic stiffness in the period of 0 to 24 hours after the radiation treatment. These changes were reversed in the subsequent 24 hour period, and remained so 3 weeks following irradiation. These findings suggest an acute mechanism behind endothelial impairment associated with whole-body, high-dose irradiation. Further research is required to ascertain the exact nature of that mechanism.