Depressed growth of Morris hepatomas in altitude- and heat-stressed but not in cold-stressed buffalo rats.
Female inbred BUF rats bearing Morris hepatomas 5123C, 5123D, 7795, and 7800 bilaterally in the femoral musculature were exposed for 3 weeks to ether 4,500-m simulated altitude or sea level or to an ambient temperature of either 7, 23, or 33 degrees C. Rats were given inoculations 12 days before these exposures. Tumor size, body weight, food consumption, and body temperatures were measured weekly in these treated rats and in normal rats. At time of killing, tumor mass, DNA synthesis (by [3H]thymidine incorporation), and respiration (by conversion of [1,4-14C]succinic acid to 14CO2) were measured in each of the 4 hepatoma lines, in the livers of normal and host rats, and in regenerated livers 10 days post 70% hepatectomy. Growths of all 4 tumors and regenerated livers were significantly impaired in rats stressed by exposure to altitude and heat but not to cold. Neither DNA synthesis nor respiration was altered in the hepatomas and livers by any environmental stress. The environmentally stressed rats gained weight at a slower rate and consumed less food than did their controls, but no differences were found in these variables for tumor-bearing and non-tumor-bearing rats. However, whereas the ratio of body weight gain to food consumed was reduced under the three stressful environments, that of tumor weight gain to food consumed was not altered by any environment. Host survivorship was not influenced by any of these effects.