Effects of low-dose gamma-irradiation to the chest regions on the blood pressure of spontaneous hypertensive rats.

We examined changes in the blood pressure and the superoxide dismutase (SOD) activities in aortic tissue after gamma-irradiation to the chest regions of spontaneous hypertensive rats (SHR) and Wistar Kyoto rats (WKY), and obtained the following results. After 5 Gy irradiation, there was no change with time in the blood pressure in WKY rats, while a transient decrease (3 days later) was observed in SHR rats. The Cu/Zn-SOD activity in the aorta of SHR was less than that of WKY. 5 Gy irradiation induced an increase in the Cu/Zn-SOD activity in SHR nearly to the level observed in WKY, which remained unchanged upon irradiation. Therefore, unlike high-dose irradiation, irradiation at a relatively low-dose of 5 Gy to SHR appears to increase the aortic Cu/Zn-SOD activity, which is lacking in SHR, leading to a decrease in the blood pressure.