Hypoxic suppression of dietary-induced component of resting metabolism in rats

Wistar rats fasted for 48 h were exposed to hypoxia (9.5% O2 in N2) at ambient temperatures (Ta) of 13.5, 24.5, and 32.0 degrees C. In normoxic environment, fasted rats showed significantly lower values of oxygen consumption (VO2), dry heat loss (R + C + K), and colonic temperature (Tcol) than in fed counterparts. The extent of decrease in each parameter was nearly same at any Ta. On exposure to hypoxia, fed rats showed a significant decrease in VO2, (R + C + K), and Tcol at any Ta. The decrease was particularly great at Ta 13.5 degrees C. In contrast to fed rats, fasted rats showed a significant decrease in all of these parameters only at Ta 13.5 degrees C. No such decrease was observed at Ta 24.5 and 32.0 degrees C. However, a significant difference in Tcol was found at Ta 24.5 degrees C in fasted rats between normoxic and hypoxic environments. Moreover, there was no statistically significant difference between fed and fasted rats in each parameter at any Ta in hypoxia. These results suggest that hypoxia suppresses both dietary-induced and cold-induced components of metabolism in rats.