Stimulatory effect of high polyunsaturated fat diet on lung metastasis from the 13762 mammary adenocarcinoma in female retired breeder rats.

The effect of a high-fat (HF) diet (23% corn oil) on the growth and metastasis of the 13762 mammary tumor in Fischer 344 retired breeder (RB) and young virgin (YV) female rats was studied. The RB (10-12 mo old) and YV (8 wk old) rats were fed the HF or low-fat (LF) diet (5% corn oil) prior to and following tumor implantation for a total of at least 10 weeks. The growth rate of the primary tumor in the intact RB and YV was not affected by the HF diet. In RB rats ovariectomized 4 weeks prior to tumor implantation, the tumor grew significantly faster in the HF group as compared to the LF group. The total volume of metastatic tumor nodules in the lungs of the HF groups was significantly higher than that in the the lungs of the LF groups in both the intact and ovariectomized RB. In the YV, there was no difference in pulmonary metastatic burden between the HF and LF groups. The weights of the HF intact and ovariectomized RBs were higher than those of the LF animals. However, when pulmonary metastatic tumor burden was compared to body weight at implant or at sacrifice, there was no significant correlation in either the HF or LF groups. These results suggest that an HF diet enhanced the growth of pulmonary metastases in the intact and ovariectomized RB but not the YV rats and that the effect of the HF diet on pulmonary tumor burden cannot be attributed entirely to increased body weight.