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Increased Survival of Rats Bearing Morris Hepatoma 7800 after Induction of Hypothyroidism¹

Department of Medicine, Royal Victoria Hospital and McGill University Clinic, Montreal, Quebec H3A 1A1 [S. M., M. A. Y., P. V. N. M.], and Department of Biochemistry, Howard University School of Medicine, Washington, D. C. 20060 [H. P. M.]

The survival of Buffalo rats bearing Morris Hepatoma 7800 was increased significantly (23 to 31%) after induction of hypothyroidism by propylthiouracil (PTU) (0.1% in Purina rat chow) or ¹³¹I. The concentration of PTU used was in the optimal range as 0.03% PTU was less effective than 0.1%, while 0.4% PTU appeared to be toxic. Exogenous thyroxine (8 µg/kg body weight) reversed the effects of PTU and actually shortened survival. Because food consumption and body weights of hypothyroid rats were decreased, the survival of pair-fed controls was studied and found to be the same as in untreated controls. We conclude that the hypothyroid state increases the survival of rats bearing Morris Hepatoma 7800. We have not yet been able to define any anatomical or biochemical parameters which may be responsible for this effect.

¹ Supported by grants from the Canadian Medical Research Council (MA 5474), Charles Frosst Co., Ltd., and USPHS (Grant Ca 10729).

² Recipient of a Chercheur-Boursier award of the Quebec Medical Research Council. To whom requests for reprints should be addressed, at Division of Gastroenterology, Royal Victoria Hospital, 687 Pine Avenue West, Montreal, Quebec, Canada H3A 1A1.

Received 8/14/78. Accepted 3/22/79.