The irradiation-associated decline in the in vivo uptake of glucose observed in rats fed fish oil is prevented by feeding a diet enriched in saturated fatty acids.

Previous in vitro studies have shown that abdominal irradiation diminishes the uptake of many nutrients and that the extent of this effect can be modified by varying the type of dietary fatty acid. This study was undertaken to determine (1) the effect of dietary fish oil fatty acids (FO) on the in vivo absorption of D-glucose and (2) the effect of feeding isocaloric diets containing FO or beef tallow (BT) on the in vivo uptake of glucose 2 weeks after a single 600 cGy exposure to abdominal irradiation from a 137Cs source. Feeding FO reduced the jejunal and ileal maximal transport rate (Vmax) and Michaelis constant (Km) for glucose uptake in nonirradiated control animals. In irradiated rats the Vmax was higher and the Km was lower in animals fed BT than in those fed FO. The passive component of glucose uptake was higher in control rats fed FO than in those fed BT yet was lower in irradiated animals fed FO compared with those fed BT. Although the value of the Km fell with FO, the effective resistance of the intestinal unstirred water layer rose so that the uptake of lower concentrations of glucose was undisturbed. However, FO reduces the uptake of higher concentrations of glucose as a result of a decline in the value of the Vmax that is sufficiently large to override the enhanced passive permeability of the intestine to glucose.(ABSTRACT TRUNCATED AT 250 WORDS)