ラード投与ラットにおける血中レトリプトファンの消失に及ぼす血清遊離脂肪酸レベルの影響

抄録

In rats fed a 40% lard-containing diet for 2 h after fasting for 24 h, the concentration of free fatty acid, or nonesterified fatty acid (NEFA) in serum was about 1, 600μEq/l, which was about four times higher than that of rats fed a control diet. This lard-diet feeding increased the concentration of free L-tryptophan (Trp) in the serum, but did not affect the serum total Trp and albumin concentrations, or Trp concentration and tryptophan 2, 3-dioxygenase activity in the liver. When the relationship between NEFA and free Trp concentration in the serum was checked, there was a significant positive correlation between the two. The rate of increase of free serum Trp concentration was much higher at serum NEFA concentrations exceeding 1, 000μEq/l than at concentrations of less than 1, 000μEq/l. When control and lard-fed rats were injected i. v. with a Trp solution (100μmol/kg BW), the disappearance rate of total blood Trp in the lard-fed group was significantly higher than that in the control group at 0.5, 1, and 3 min after the injection, but there was no difference in the rate between the two groups thereafter. When the control and lard-fed rats were injected i. v. with a Trp solution (100μmol/kg BW) containing [3H] Trp, there was no difference in radioactivity in the liver, brain, kidney, spleen, and muscle between the two groups 10 min after the injection. These results suggest that under physiological conditions (ca. 100 prvi Trp and 4% albumin), an increase in free serum Trp concentration subsequent to an increase in the serum NEFA level does not have a large influence on the transport of Trp into the liver.