Fernstrom M H, Fernstrom J D
Department of Psychiatry, University of Pittsburgh School of Medicine, Western Psychiatric Institute and Clinic, PA 15213.
Life Sci. 1993;52(11):907-16. doi: 10.1016/0024-3205(93)90525-8.
The effect of meal-induced changes in serum free tryptophan (TRP) levels on brain TRP levels was examined in streptozotocin-diabetic rats. Diabetic rats, fasted overnight, were given free access to a non-protein food containing either no fat or large amounts of fat (45% by weight), and were killed 1, 2 or 3 hr thereafter. Ingestion of the high-fat meal produced large increases in both serum non-esterified fatty acid (NEFA; 2-fold) and free TRP levels (2.5-fold), but no increments in cerebral cortical or hypothalamic TRP levels or in the rate of serotonin synthesis in these brain regions. Because the rats were diabetic, serum levels of the other large neutral amino acids (which compete with TRP for transport into brain) did not vary from fasting values in any of the treatment groups. There thus was no uncontrolled variation in the competitive transport of TRP into brain that might have obscured potential effects due to the alterations in serum free TRP levels. The results add further evidence to the notion that TRP transport into the central nervous system is not influenced by the size of the free TRP pool in blood.
在链脲佐菌素诱导的糖尿病大鼠中，研究了进食引起的血清游离色氨酸（TRP）水平变化对脑内TRP水平的影响。将过夜禁食的糖尿病大鼠自由给予不含脂肪或含有大量脂肪（45%重量比）的非蛋白质食物，然后在1、2或3小时后处死。摄入高脂肪餐导致血清非酯化脂肪酸（NEFA；增加2倍）和游离TRP水平（增加2.5倍）大幅升高，但这些脑区的大脑皮质或下丘脑TRP水平以及血清素合成速率没有增加。由于大鼠患有糖尿病，其他大型中性氨基酸（与TRP竞争转运到脑内）的血清水平在任何治疗组中均未偏离禁食值。因此，TRP向脑内的竞争性转运没有不受控制的变化，这种变化可能掩盖了血清游离TRP水平改变所产生的潜在影响。这些结果进一步证明了以下观点，即TRP向中枢神经系统的转运不受血液中游离TRP池大小的影响。
