Changes in incorporation of [3H]thymidine into DNA of rat skin following cutaneous application of dibutyltin, tributyltin and 1-chloro-2:4-dinitrobenzene and the relationship of these changes to a morphological assessment of the cellular damage.

[ 3 H]thymidine is incorporated into DNA from epidermal and dermal slices of untreated dorsal skin at similar rates. Treatment of dorsal skin with dibutyltin (67 nmoles/sq cm) stimulated the incorporation of the nucleoside into DNA from both preparations (relative to zero time controls) but the greater increase incurred into DNA from epidermal slices. Single cutaneous applications of different applied doses of dibutyltin, tributyltin, and 1-chloro-2: 4-dinitrobenzene altered the incorporation of [ 3 H]thymidine into DNA of epidermal slices from the treated skin in a complex manner. Doses which produced minimal damage (as assessed histologically) stimulated the incorporation above zero time controls while doses producing moderate damage inhibited at early times and stimulated later. Doses which produced marked damage, not surprisingly, resulted in a marked and prolonged inhibition of incorporation. The increased incorporation of [ 3 H]thymidine does not correlate with the degree of cellular damage as presently assessed histologically but does indicate the sensitivity and thus potential usefulness of biochemical parameters since considerable stimulation of thymidine incorporation was observed at times when minimal morphological changes were observed.