Systemic blood pressure after X-ray irradiation of rats at 6 months and 6 weeks of age. Systolic, mean and diastolic pressure of rats after 6.0, 8.0 or 10.0 Gy X-ray irradiation. Data are mean ± SD, n=8/group. *P < 0.05, **P < 0.01 and ***P < 0.001.