[Myocardium of mdx mice contains factor(s) that damage DNA structure and retard DNA reparation after gamma-irradiation (experiences in modeling system)].

We studied the action of saline extracts of ventricle myocard (EM) of C57BL and mdx mice on DNA structure and repair of one-strand breaks of DNA in a modelling system. The system involves DNA repair in E. coli WP2 cells after gamma-irradiation. Using standard technique, DNA reparation was estimated on measuring the speed of E. coli DNA sedimentation in alkaline sucrose gradients. It was shown, that EM of C57BL or mdx mice exerted no influence on DNA repair, which was completely declined within 60 min with EM present in the growth medium of permeabilized E. coli. Addition of C57BL mice EM into lytic solution does not accelerate DNA sedimentation of nonirradiated E. coli. At the same time, EM of mdx mice sharply accelerates DNA sedimentation of nonirradiated E. coli reducing DNA molecular weight from 200 x 10(6) to 135 x 10(6) Da. At entering in the lytic solution the EM of mdx mice also slows down E. coli DNA repair after gamma-irradiation. It is supposed, that EM of mdx mice may contain a factor(s) damaging DNA in the E. coli lysate and presumably slowing down DNA reparation after gamma-irradiation. Russian Foundation of Basic Research Grants 99-04-49390, 02-04-49870 and 00-04-49390.