Rates of triolein absorption in suckling and adult rats

To determine the extent to which suckling animals differ from adults in their capacity to absorb fat, we compared the rate of absorption of orally administered [14C]triolein in 11- to 12-day-old suckling rats with that of 10-wk-old adults by three distinct methods. In the first, the rate of [14C]triolein disappearance was determined by quantitating substrate remaining in the gastrointestinal tract after oral administration. In the second, 14CO2 expiration in breath was measured continuously for 6 h after an identical feeding. In the third, intestinal triglyceride output was estimated by the lipoprotein lipase inhibitor, Triton WR-1339. Triolein disappearance, 14CO2 excretion, and intestinal triglyceride output were two- to threefold higher in suckling rats compared with adults (P less than 0.01, P less than 0.0001, and P less than 0.01, respectively). There was also a highly significant linear relationship between 14CO2 excretion and both triolein disappearance and intestinal triglyceride output for both age groups (P less than 0.0001 and P less than 0.003, respectively). These data show that consistent with its high dietary intake, the suckling rat can absorb triolein at rates significantly higher than the adult.