The trachea-larynx, thymus gland, cervical lymph nodes, submaxillary salivary glands, and diaphragm of 54–88 pairs of twin albino rats, one twin inoculated and the other twin not inoculated with Walker carcinosarcoma 256, were weighed and analyzed for lipid and water levels expressed as gm/100 gm nonlipid dry weight. The tumors varied from one to 153 (average 52) per cent of host weight.

There was a loss of fresh, wet weight in all five tissues of tumor-bearing animals, averaging from 9 per cent (P = 0.001) in the trachea-larynx to 43 per cent in the thymus gland.

In all five tissues of the nontumor-bearing twins, the mean water, total cholesterol, ester cholesterol, free cholesterol, and phospholipid levels were significantly (P = 0.01 or less) lower, and the neutral fat levels higher, than those of Walker carcinosarcoma 256, with the exceptions of the submaxillary salivary glands, in which free cholesterol and phospholipid levels were in the low range of those in the tumor. Phospholipid levels were on the average the least different and neutral fat levels the most different from those of the tumor.

In all five tissues of tumor-bearing twins there were significant increases in the mean levels of water, total cholesterol, and free cholesterol and in two tissues of ester cholesterol and phospholipid. In three tissues there were significant declines in the mean level of neutral fat. In over 80 per cent of the instances where shifts were possible, the water and lipid levels of all five tissues in the tumor-bearing animals became more uniformly like the composition of Walker carcinosarcoma 256.

The sex of the albino rat was practically without effect upon these shifts in water and lipid levels.

The shifts in the tumor-bearing animals appeared most commonly in animals with tumors which had grown at the average rate of 1 per cent or more of host weight per day or which weighed 20 per cent or more of host weight. In thymus gland, and occasionally in cervical lymph nodes, the shifts pyramided in animals bearing tumors which weighed about 40 to 50 per cent of host weight, the shifts in animals bearing larger tumors being less marked.

These results indicate further that tissues of albino rats develop a sameness of lipid and water levels, like those of the tumor, as Walker carcinosarcoma 256 grows upon the host rat.

*

A paper upon this work was presented before the tumor section of the Federation of American Societies for Experimental Biology, Atlantic City, April, 1956.

This work was supported by a grant from the National Cancer Institute of Canada.

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