Male Swiss albino mice, 6-8 weeks old and weighing 26.9 ± 2.54 g, were selected from an inbred colony maintained under controlled conditions of temperature (23 ± 2°C), humidity (50 ± 5%) and light (10 and 14 h of light and dark). The animals were given sterile food (wheat 70%, Bengal gram 20%, fishmeal 5%, yeast powder 4%, sesame oil 0.75% and shark liver oil 0.25%) prepared in the laboratory and water ad libitum. Throughout the experiment 5-6 animals were housed in a polypropylene cage containing sterile paddy husk (procured locally) as bedding.

One group of animals was fed orally (using 22 gauge oral feeding needles) with a 5% dextrose solution once a day for 7 days before irradiation and served as the control group, while the other mice received 500mg/kg b.wt. of Liv.52 powder (supplied by The Himalaya Drug Company) in 5% dextrose solution in a similar fashion. One hour after administration on day 7, the animals of both groups were exposed to 4.5Gy of g-radiation (Gammatron telecobalt therapy source) in specially designed well-ventilated plastic boxes. The animals were irradiated in groups of 10 at a dose rate 0.88 Gy/min., at a distance of 60 cm from the source (dosimetry done by Dr. J.C.R. Solomon, Department of Radiotherapy and Oncology, K.M.C. Manipal). For comparison a few animals were also treated with 5% dextrose and Liv.52 as above but without irradiation.

Animals from each group were given 0.025% colchicine intraperitoneally 2 h before killing. The animals from each group were killed by cervical dislocation at ¼, ½, 1, 2, 3, 7 and 14 days post exposure. The femora were removed and the metaphase plates were prepared by the usual cytogenetic method. The slides were stained in 4% Giemsa at pH 6.8 The chromosomal aberrations (chromatic and chromosomes) were scored on an AO Reichert Microse at a magnification of 500 x. Four hundred metaphase plates were scored from each animal and a total of 2000 metaphase plates were scored for 5 animals at each post-irradiation time. The criteria for scoring were based on the classification of Savage (1975).

The data were analysed by the chi square test on an IBM computer.

The results are expressed as aberrations/100 cells. Liv.52 administration did not affect the control frequency of aberrations (Table 1).

The frequency of aberrant cells increased from day ¼ reaching to a peak level on day ½ in both the irradiated and Liv.52 + irradiated groups and declined thereafter. The frequency of aberrant cells was significantly less in the Liv.52 + irradiated group than in the irradiated group (Table 1).

Chromatid breaks were seen at day ¼, which continued to increase up to day ½ and decline thereafter. The normal levels were restored on days 14 and 2 in the irradiated and Liv.52 + irradiated group respectively (Table 1).

Chromosome breaks, centric rings, dicentrics and chromosome exchanges were observed at day ½ post exposure in both groups. The frequency of chromosome breaks and centric rings was highest on day 1, while that of dicentrics and exchanges was highest on day ½ and declined thereafter. The aberration frequency was always lower in the Liv.52 + irradiated group than in the irradiated group (Table 1).

The highest frequency of total aberrations was recorded on day ½ in both groups, thereafter it declined continuously up to day 14 post irradiation. The percentage of total aberrations was significantly lower in the Liv.52 + irradiated group up to day 7 than in the irradiated group (Table 1).

Pulverized cells increased from day ¼ and the highest number of these cells was recorded on day 1; thereafter pulverized cells could not be observed. The frequency of pulverized cells was significantly lower in the Liv.52 + irradiated group than in the irradiated group (Table 1).

Liv.52 has been reported to protect mice against radiation-induced sickness, dermatitis and spleen injury (Saini et al, 1984a,b). The administration of Liv.52 prior to irradiation resulted in a significant decline in chromosomal aberrations (Table 1). The frequency of aberrant cells was significantly lower in the Liv.52 + irradiated group than in the irradiated group at all post-exposure time periods studied. Gupta and Uma Devi (1985, 1986) and Thomas and Uma Devi (1987) have also reported a decline in aberrant cells in mice treated with MPG and WR-2721, singly or in combination, before exposure to g radiation.

Liv.52 was equally effective in protecting the chromosomes against radiation-induced damage, as is evidenced by the lower frequency of chromatic breaks, chromosome breaks, centric rings, dicentrics, exchanges, acentric fragments and total aberrations. Most of these aberrations had returned to the normal level at day 3 post exposure in the Liv.52 + irradiated group as compared to the irradiated group. These findings support our earlier report on micronuclei, where the frequency of micronuclei in the Liv.52 + irradiated mice returned to a normal level at day 3 post exposure (Jagetia and Ganapathi, 1989).

The frequency of pulverized cells was always significantly lower in the drug-treated group than in the irradiated group. This indicates that Liv.52 could protect the cells against the severe infliction of radiation damage.

The exact mechanism by which Liv.52 prevents chromosomal damage is not known. The depletion of intracellular glutathione (GSH) has been reported to be one of the causes of radiation-induced damage, while increased levels of intracellular GSH are responsible for radioprotective action. A similar mechanism of action may be attributed to the radioprotective action of Liv.52, which has been reported to restore the intracellular GSH level to normal in rats exposed to 4.0 Gy of g radiation (Sarkar et al., 1989).

There is growing evidence that double-strand breaks (dsb) are mainly responsible for the formation of chromosomal aberrations (Natrajan et al., 1980; Bryant, 1988). It is possible that the elevated levels of GSH in the Liv.52-treated group may be able to enhance the repair of dsb, lowering the frequency of chromosomal aberrations in this group. This conclusion is supported by the recent study of Ochi (1989) who has reported that chromosomal aberrations were repaired only in GSH-positive cells.

We acknowledge with thanks the financial support extended by The Himalaya Drug Company, to carry out this work. The irradiation facilities provided by the Head, Department of Radiotherapy and Oncology, KMC, Manipal are thankfully acknowledged. We also wish to thank Mr. Harischandra Nayak of Computer Department, KMC, Manipal for chi-square analysis.