Effect of pre-irradiation of mice whole-body with X-ray on radiation-induced killing, induction of splenic lymphocyte apoptosis, and expression of mutated Ca2+ channel α1A subunit

This study examined radiosensitive and radioadaptive responses following whole-body irradiation in rolling mouse Nagoya (RMN) which carries the mutation in the gene coding for the U I A subunit of P/Q-type Ca2+ channel. Adult RMN and littermate controls (C3Hf/Nga) were subjected to a single exposure of X-irradiation at doses of 4, 5, and 6.75 Gy. RMN were slightly radiosensitive as compared to the control mice. All RMN died on day 8 after X-irradiation at 6.75 Gy, and all controls on day 13. In both RMN and controls, Bax- and TUNEL-positive lymphocytes in the splenic white pulp increased 12 h after irradiation at 3 Gy. Inductions of Bax- and TUNEL-positive lymphocytes were apparently suppressed 2 weeks following pre-irradiation with a low dose (0.45 Gy). In RMN, expression of the mutated Ca2+ channel alpha(1A) subunit was not found in the lymphocytes and was not induced by the irradiation. These results suggested that the mutation in P/Q-type Ca2+ channel might modify the radiosensitivity. This may mean that the radioadaptive response results in the depression of apoptosis in splenic white pulp lymphocytes, but not in the expression of the mutated Ca2+ channel. (C) 2002 Elsevier Science B.V. All rights reserved.