Blood sugar levels, and tumor size and incidence were determined for alloxanized Wistar rats bearing subcutaneous and intraperitoneal transplants of Novikoff hepatoma and Walker 256 carcinoma, and histological examination of the pancreas was undertaken to determine the extent of the damage to the beta-cells of the islets of Langerhans. Experiments were conducted in which animals were alloxanized 14 days, 7 days, 4 days, and 24 hours prior to, and 24 hours and 4 days after transplanting. The

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... dence and rate of growth of intraperitoneal tumors was appreciably decreased, and the rate of growth of subcutaneous tumors was slightly decreased in alloxanized animals, as compared with tumor-bearing controls. In tumor-bearing alloxanized animals, the high blood sugar levels characteristic of alloxan-diabetes were reduced to normal in some animals, and considerably ameliorated in others, as compared with alloxan-diabetic controls. Intraperitoneal tumors were more effective than subcutaneous tumors in reducing blood sugar levels, and relief was more pronounced in animals alloxanized just before or after transplanting than in those alloxanized two weeks before transplanting. Histological examination indicated that intraperitoneal tumor tissue invading the pancreas of alloxanized rats exerted a protective or regenerative effect on the beta-cells of the islets of Langerhans, which are selectively destroyed by alloxan. The possible role of sulphydryl groups in the amelioration of alloxan-diabetes in tumor-bearing animals, and in the reduction of tumor size and incidence in alloxan-diabetic animals is discussed. This work was reported in part in Proceedings of the American Association for Cancer Research, 2;20, 1955.