Pouches from three experimental and one control animal were excised for analysis at various times during the first week and thereafter each week of carcinogen application (9,10-dimethyl-1,2-benzanthracene) until the 13th week, at which time large tumors were present in all remaining animals. Histologic progression from normal through inflammation, uniform hyperplasia, localized premalignant hyperplasia, to small tumors (7 weeks) and then large squamous-cell carcinomas, was observed). Sulfhydryl group concentration, determined by amperometric titration of acid-soluble fractions of cell-free extracts of the whole pouches of males, showed a biphasic curve with an increase in -SH at 36 hours, followed by a decrease at 60 hours. Pouches from females did not exhibit the early rise, and the decrease was more profound. -SH concentrations remained low until the period of tumor production and then rose slowly in the whole pouches. Tumor tissue contained about 40 per cent of the concentration of soluble SH exhibited by the nontumor-bearing tissue from which it was removed. The latter fell within the range of control tissue.

*

This investigation was supported by grants from the U.S. Public Health Service # CS 9582 and C 4170.

Part of this work was presented at the meeting of the American Association for Cancer Research at Chicago in April, 1960.

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