Energy expenditure and motor activity in rats receiving total parenteral nutrition

Rats with intravascular catheters connected to infusion systems are frequently used in the investigation of nutritional and metabolic problems. Although the animal is often referred to as "unrestrained," there is no information on the effect of the catheter assembly or total parenteral nutrition (TPN) on total (TEE), activity (AEE), and resting (REE) energy expenditure (TEE = REE + AEE). Male Fischer 344 rats were studied in an analytical respiration calorimeter. Normal unoperated rats, aseptically catheterized orally fed rats from postoperative day 1 to 7, and TPN rats were studied. Orally fed catheterized rats had weight loss, negative nitrogen balance, negative energy balance, elevated REE, and normal AEE during the first 4 postoperative days. Their weight gain, positive nitrogen balance, AEE, and REE were almost identical to those of normal rats over postoperative days 5 through 7. REE and AEE in TPN rats were similar to values in normal rats. These data indicate that catheter operation and TPN cause no abnormality in AEE and REE if adequate time is allowed for recovery from catheter operation and strict attention is given to asepsis.