Conformational changes in the chromatin of the brain of developing rats and its modulation by zinc chloride.

Conformational changes in the chromatin of the brain were studied during the development of the rat (3-, 14- and 30-day old) using micrococcal nuclease (MCN) and DNase I. The rate and extent of digestion of chromatin by MCN is not altered during development. However, pre-incubation of slices of the cerebral cortex with ZnCl2 increases the initial rate of digestion by MCN by 2-3-fold, and also enhances the production of monomer DNA. The rate and extent of digestion of chromatin by DNase I is greater in an early stage of development. The initial rate of digestion by DNase I is stimulated by 3-4-fold after ZnCl2 treatment. These data show that changes occur in the conformation of chromatin, particularly in the internucleosomal region of brain cells as they pass from dividing to the non-dividing state.