O-6-alkylguanine-DNA alkyltransferase activity in tissues of mice treated with antischistosomal agents.

The activity of O-6-alkylguanine-DNA alkyl transferase (ATase), the enzyme responsible for repairing promutagenic methylation damage in DNA, was measured at various time intervals in tissue extracts of mice administered (in vivo) a single therapeutic dose of the antischistosomal agents hycanthone, oxaminiquine and metrifonate. In control animals, liver contained the highest levels of ATase activity (15.8+/-1.8 fmole ATase/mu g DNA) followed by spleen (11.0+/-1.7 fmole/mu g DNA), intestine (2.3+/-0.3 fmole/mu g DNA) and bladder (0.22+/-0.04 fmole/mu g DNA). With hycanthone, ATase activity was reduced by 6 and 24 h post treatment to 74% and 27% below the control value, respectively. Bladder exhibited a 25% inactivation in the ATase level at 6 h time point. Spleen and bladder did not show any alteration in the ATase activity. In animals administered oxaminiquine, liver and bladder had a near identical pattern to that observed for hycanthone. Spleen and intestine, however, revealed activation in ATase by 50% and 42%, respectively after 6 h of treatment. This activation was also observed in the bladder of metrifonate-treated mice. In a previous study (Badawi et al, Cancer Lett 75: 167, 1993), DNA-alkylation damage (O-6-methyldeoxyguanosine; O-6-MedG) was evaluated in these tissues and there was an inverse correlation between the levels of methylation damage and ATase activity in liver (r=-0.85, p<0.01), intestine (r=-0.62, p<0.01) and bladder (r=-0.59, p<0.05).