The sustained development of preneoplastic lesions depends on high protein intake.
The effects of sequential alterations in the feeding of two levels of dietary protein (5% and 20% casein) on the postinitiation development of aflatoxin B1- (AFB1) induced gamma-glutamyl transpeptidase-positive (GGT+) preneoplastic foci were examined. Weanling male Fischer 344 rats fed AIN-76A diet (20% protein) were administered 10 intragastric doses of AFB1 (1 dose/day during the 14-day dosing period excluding weekends) at 250 micrograms/kg body wt (initiation). After AFB1 tissue clearance, rats were randomly assigned to dietary treatment groups. During the next 12 weeks (promotion), they developed AFB1-induced GGT+ preneoplastic lesions. The 12-week promotion period was subdivided into four three-week periods, during which rats were fed isocaloric diets containing 20% casein during all four periods (20:20:20:20), 5% casein during all four periods (5:5:5:5), or sequentially altered casein levels (20:5:20:5 and 5:20:5:20). Rats were killed at 3,6,9, and 12 weeks to examine the dependence of GGT+ foci development on protein intake. Animals fed 5% casein diets developed significantly fewer (p < 0.01) GGT+ foci than animals fed 20% casein diets despite greater total caloric intake. Similarly, in the intervention groups, preneoplastic development was enhanced when the 20% casein diet was fed and inhibited when the 5% casein diet was fed. These results indicate that the sustained development of AFB1-induced preneoplastic foci depends on a high protein intake. Alternatively, these results suggest that low protein intake inhibits lesion development.
Youngman
L D
LD
Clinical Trial Service Unit, Radcliffe Infirmary, University of Oxford, UK.
Campbell
T C
TC
D016604:Aflatoxin B1; D000818:Animals; D001835:Body Weight; D002364:Caseins / Q000008:administration & dosage / Q000009:adverse effects; D004044:Dietary Proteins / Q000008:administration & dosage* / Q000009:adverse effects; D008297:Male; D011230:Precancerous Conditions / Q000201:enzymology / Q000209:etiology / Q000473:pathology*; D051381:Rats; D011916:Rats, Inbred F344; D005723:gamma-Glutamyltransferase / Q000378:metabolism*
D002364:Caseins; D004044:Dietary Proteins; D016604:Aflatoxin B1; D005723:gamma-Glutamyltransferase