Effects of high levels of dietary fats on the growth of azaserine-induced foci in the rat pancreas.

Azaserine induced two phenotypically different populations of foci, namely, acidophilic and basophilic foci. The effects of dietary modification during the post-initiation phase of carcinogenesis were examined. A diet of 20% (w/w) unsaturated fat (unsat) compared to a 20% saturated fat (sat) diet or a control diet (5% unsaturated fat) increased the number of acidophilic foci, as well as the thymidine labeling index (LI) of their nuclei. While the basophilic foci are carcinogen-induced and at 2.5 mo post-initiation have a similarly high growth rate to the acidophilic foci, this rate is not sustained as indicated by examination of both the LI and mean size of foci at 4 mo post-initiation.