No abstract

Selenium (Se) toxicity and utilization was evaluated in hamsters fed casein- and torula yeast-based diets. 4-week-old hamsters received semipurified diets for 21 days. In experiment I diets were supplemented with either 0.25, 10, 20, 40 or 80 ppm Se as sodium selenite (SS) and in experiment II diets were supplemented with 0.1 5.0 or 10.0 ppm as SS or selenomethionine (SM). Blood and tissue Se concentrations and glutathione peroxidase (GSH-Px) activity were measured at the termination of the feeding period. In both studies growth rate was depressed and food consumption decreased in hamsters given diets supplemented with 10 ppm or greater SS. Mortality associated with Se toxicity occurred only in females fed the 80 ppm Se-supplemented diet. Whole blood and tissue Se concentrations rose with increasing dietary Se and occurred up to the 80 ppm Se level in blood. Liver, kidney and lung Se concentrations were higher in hamsters fed SM than for those fed SS. Plasma GSH-Px activity was not significantly affected by increasing dietary Se levels, and hamsters fed dietary Se levels above 10 ppm did not have increased erythrocyte GSH-Px activity associated with increased blood Se concentrations. Liver GSH-Px activity was higher in SM-fed hamsters. The results suggest that dietary Se, fed as SS, becomes toxic for Syrian hamsters at levels of 10 ppm and above.

We previously reported an enhancement of pancreatic carcinogenesis induced by N-nitrosobis(2-oxopropyl)amine (BOP) in hamsters fed diets containing high levels of corn oil. The research presented here compared diets high in corn oil with those high in beef tallow in the enhancement of pancreatic carcinogenesis. Pancreatic cancer was induced with 20 mg BOP/kg body wt, s.c. administered at 8 weeks of age. One week later, hamsters were assigned to one of five diet treatments: (i) 4.3% corn oil (control); (ii) 20.5% corn oil (high corn oil); (iii) 0.5% corn oil + 3.8% beef tallow (low beef tallow); (iv) 0.6% corn oil + 19.9% beef tallow (high beef tallow); and (v) 5.1% corn oil + 15.4% beef tallow (high fat mixture). These diets were fed until the study ended 84 weeks after BOP treatment. Hamsters were trained through pair feeding to consume the same calorie allotment as the control corn oil group. By the end of the experiment, BOP-treated hamsters that were fed diets containing beef tallow were consistently heavier than those fed corn oil. Survival was longer in hamsters fed the high-beef tallow and high-fat mixture compared with the other diet groups. Tumor data were age adjusted to correct for survival differences. Pancreatic adenoma incidence and multiplicity (no./effective animal) were higher in hamsters fed beef tallow than those fed corn oil diets. Carcinoma in situ multiplicity was elevated in hamsters fed high-fat diets irrespective of the nature of fat fed. Pancreatic adenocarcinoma multiplicity was elevated in hamsters fed the low- or high-beef tallow diets compared with the low- or high-corn oil diets. The mixture of fat resulted in an intermediate yield.

Syrian hamsters were fed torula yeast (TY) diets with 8 selenium (Se) supplement levels (0.0-10.0 ppm Se as sodium selenite) or casein (C) diets with 5 supplement levels (0.0-5.0 ppm Se as sodium selenite) for 25 weeks. Whole blood Se, plasma glutathione peroxidase (GSH-Px) activity and erythrocyte GSH-Px activity were measured after 5, 10, 15 and 25 weeks. At 25 weeks hematology was examined and tissue samples analyzed for Se and evaluated for histopathological lesions. While survival was not influenced by dietary Se, food consumption and body weight gain were altered in animals given TY, as those fed 0.0, 0.05 or 10.0 ppm Se consumed less diet. Weight gains at 25 weeks were highest in animals at the 0.1 ppm Se level and reduced in those given unsupplemented TY or 10.0 ppm Se supplements. Hemoglobin, hematocrit and red blood cell counts were reduced in females fed the lowest and highest Se supplements with TY diets. With both C and TY, whole blood Se rose with increasing dietary Se and in the case of TY, Se was elevated with each feeding increment, except between the 0.05 and 0.1 ppm or the 0.25 and 0.5 ppm levels. Plasma GSH-Px increased with rising Se up to 10 ppm, and erythrocyte GSH-Px activity increased up to 5 ppm Se. Erythrocyte GSH-Px values were higher in animals fed C diets. Histopathological observations were normal at all Se levels. Syrian hamsters tolerated dietary Se from 0.05 to 5.0 ppm Se for 25 weeks of observation without detrimental effects.