THE EFFECT OF THE RATE AND ROUTE OF NUTRIENT DELIVERY ON TOTAL-BODY AND ORGAN COMPOSITION IN RATS

To assess the effects of administering increasing rates of total paren teral nutrition (TPN) on total-body and organ composition, infusion ca theters were implanted aseptically into the right jugular vein of Spra gue-Dawley rats. Animals received 14 d of either a high (H), medium (M ), or low (L) rate of TPN infusion (1.22, 1.49, 1.74 MJ . kg(-1)BW . d (-1) and 1.74, 1.48, 1.22 gN . kg(-1)BW . d(-1), respectively; 1:1 lip id:glucose energy), or the TPN solution orally (O TPN group). Weight-m atched (w) chow-fed (c) animals were sacrificed at the same final weig ht as the L TPN and O TPN groups (190 g, LWC group), or the M and H TP N groups (250 g, HWC group). There were 5 animals in each group. The r ates of body weight increase of the M TPN, H TPN, and HWC groups were similar (p > 0.05) and greater than the L TPN and O TPN groups (p < 0. 001). The L TPN and O TPN groups who received similar amounts of nutri ents had similar rates of weight gain. Total body lipid expressed as a percentage of body weight was significantly greater (p < 0.01) in the L, M, and H TPN groups compared to the orally fed groups. The proport ion of water and protein in the fat-free wet weight were similar for a ll groups (p > 0.05). The lipid content of the liver as a percentage o f its weight was greater (p < 0.05) in the orally fed groups. There wa s no significant difference in the percentage of water or protein of i ndividual organs or the total viscera between any group. These finding indicate that: (a) TPN administration can maintain similar rates of p rotein and water deposition compared to normal growth-maintaining oral diets; (b) there is an effect of route of TPN administration on lipid deposition in adipose tissues; and (c) infusion of a glucose/lipid TP N regimen at rates in excess of requirements for growth in rats promot es lipid deposition in adipose tissues rather than visceral tissues.