Pharmac. 7"her. Vol. 39, pp. 323 to 325, 1988 0163-7258/88 $0.00+0.50 Printed in Great Britain. All rights reserved Copyright © 1988 Pergamon Press plc Symposium Editors: J. F. WEISSand M. G. SIMIC Brief Communication EFFECT OF SUPEROXIDE DISMUTASE ON X-RAY INDUCED CHROMOSOME ABERRATIONS AND CELL CYCLE DELAY IN MUNTJAC LYMPHOCYTES A. CHATTERJEE and M. JACOB-RAMAN Cytogenetics Laboratory, Department of Zoology, Banaras Hindu University, Varanasi - 221 005, India With the advent of 5-bromodeoxyuridine-labelling and the fluorescence plus Giemsa (FPG) staining techniques (Perry and Wolff, 1974) the lymphocyte culture system has been more suitable for radiation dose-response and dose-modification studies. In spite of this, very few studies are available regarding the radioprotective action of superoxide dismutase (SOD) on mammalian lymphocytes irradiated in vitro. In human Go lymphocytes, the protective effect of SOD with respect to radiation-induced chromosome aberrations was reported (Nordenson et al., 1976; Nordenson, 1977, 1978; Chatterjee and Jacob-Raman, 1986). At 135 roentgens (R), Nordenson (1978) found insignificant reductions in frequencies of all types of aberrations due to their overall low yield. Moreover, the influence of SOD on cell cycle kinetics was not considered at all earlier. However, reduced glutathione (GSH), a well known radioprotector, was reported to restore the frequency of second cycle metaphases, lowered by X-rays, to normal levels in muntjac lymphocytes (Chatterjee and Jacob-Raman, 1986). This suggested the possibility that chemical radioprotectors might alter the radiation-induced cell cycle delay. Therefore, further information in this regard will be critical in evaluating the protective efficiency of a chemical, since shifts in cell cycle kinetics can affect the frequency of aberrations because of the reported existence of differential radiosensitivity of different subpopulations of lymphocytes (Beek and Obe, 1976). The present study was carried out by using the FPG technique, with the objectives of finding out whether exogenous addition of SOD affects the production of all types of aberrations uniformly or otherwise and the influence of SOD on cell cycle progression. Peripheral blood was drawn periodically from two adult male muntjacs (Muntiacus muntjak) (2n -- 7o'; 6q~) 2-3 hr before setting up cultures. In the case of pretreatment, SOD (15, 120 #g/rnl) (Sigma, U.S.A.) was added 30 min before X-irradiation (2-4 Gy; 110 kV, 4 mA, at 21 cm distance with 1 mm A1 filter; dose rate 1 Gy/min), and for post-treatment, SOD was added to the blood just after X-irradiation at 37°C. Cultures were set up according to standard protocol (Chatterjee and Jacob-Raman, 1986). Aberrations were scored from first cycle metaphases. Results obtained from pretreatments and post-treatments with SOD in combination with radiation are presented in Table 1. SOD pretreatment reduced the frequency of deletions significantly but not of exchanges induced by 2 Gy of X-rays. The frequency of aberrant metaphases also showed significant reduction (Table 1). However, SOD post-treatment with 2 Gy did not show significant reduction in frequencies of deletions or of aberrant metaphases, though the tendency of reduction was clear. In SOD pretreatments and post-treatments, deletions have again emerged as the category that shows maximum protection, as was observed for GSH (Chatterjee and Jacob-Raman, 1986), and the lack of protection of rearrangements induced by 2 Gy in muntjac lymphocytes is not in agreement with the reported effect of cysteine and other sulfhydryl agents on human lymphocytes where the frequency of rearrangements is reduced significantly (Edgren, 1970; Sasaki and Matsubara, 1977). The probable reason for this may be that the number of rearrangements produced in muntjacs by X-irradiation is much lower than that in humans. Interestingly, SOD pretreatment with 4 Gy enhanced the frequency of all 323