CHRONOTOXICOLOGICAL EFFECT OF METHYL MERCURY IN RAT SUBMANDIBULAR-GLAND - IMMUNOHISTOCHEMICAL CHANGES OF R-EGF, S-100 PROTEIN AND KERATIN

The effect of toxicity of methyl mercury was investigated in the subma ndibular gland (SMG) of adult male rats subjected to 12 h light dark c ycle (6 a.m. to 6 p.m. light/resting phase; 6 a.m. to 6 p.m. dark/acti ve phase). Two groups of rats received a defined dose of methyl mercur y hydroxide at seven different time points during the active (dark) an d resting (light) phase over a 24 h period. After 10 d, the rats were killed at 9 a.m. and 9 p.m. in the resting and active phase, respectiv ely. The immunohistochemical distribution pattern of epidermal growth factor (r-EGF), S-100 protein and K8.12 keratin were studied in granul ar convoluted tubules (GCT). Those rats which received injections duri ng the active phase (6 p.m. to 6 a.m.), showed stronger reactivity for r-EGF; however, the reactivity for S-100 protein was unchanged. On th e contrary, in both groups, GCT cells showed intense staining for K8.1 2 keratin. It is concluded that the detoxification mechanism of mercur y appears to be dependent on the chronobiological oscillation pattern of the GCT and their substructures.