Effects of temperature on in vitro palmitic acid uptake by chicken and rat intestinal tissue

The intestinal absorption of fatty acids proceeds by simple or facilitated diffusion, a mechanism which is affected by temperature. However, most studies in this field have not taken into consideration the fact that birds have higher physiological temperature than mammals, the absorption being studied at 37 degrees C in both cases. The aim of this work has been to find out whether the higher palmitic acid (PA) uptake rate in birds (chickens) compared to mammals (rats) is attributable to the differences between their body temperatures (41.5 degrees C for chickens and 37.5 degrees C for rats). PA-uptake was studied in intestinal (ileal and jejunal) tissue samples of both Hybro broiler chickens (male and female, 4 weeks-old) and Ico:OFA rats (males and females, 8 weeks-old). The intestinal tissue samples were incubated in micellar solution (0.6 mM 14C-PA; 0.3 mM monoolein; 3.4 mM sodium taurodeoxycholate) at 37.5 degrees C and 41.5 degrees C in both cases. Chicken intestinal tissue incorporated PA with higher efficiency at 41.5 degrees C than at 37.5 degrees C. In contrast, increasing the incubation temperature to 41.5 degrees C led to a decrease in PA uptake by female rat intestinal tissue whereas specimens from male rats exhibited the same absorptive efficiency. These results suggest that the incubation temperature determines to some extent the efficiency of fatty acid uptake. However the fact that the temperature caused opposite effects in rats and chickens indicates that the changes in temperature affect the intracellular processing of the fatty acids already taken up rather than the diffusion of fatty acids through the enterocyte brush-border membrane.