Table 4.
Preprandial and postprandial brain and postprandial plasma amino acids in rats placed on a low-protein diet
| Cerebrospinal Fluid |
Plasma |
|||||
|---|---|---|---|---|---|---|
| Preprandial |
Postprandial |
Postprandial |
||||
| Time/Diet | NP | LP | NP | LP | NP | LP |
| Arginine | 1.5 ± 0.3 | 1.4 ± 0.4 | 2.0 ± 0.1 | 1.3 ± 0.3# | 87.8 ± 3.6 | 89.3 ± 5.1 |
| Histidine | 2.0 ± 0.5 | 1.3 ± 0.3 | 2.2 ± 0.6 | 1.2 ± 0.3 | 53.3 ± 3.8 | 54.7 ± 2.8 |
| Lysine | 8.4 ± 0.8 | 6.2 ± 1.5 | 9.5 ± 0.5 | 6.2 ± 1.0* | 362.1 ± 16.4 | 312.0 ± 53.7 |
| Methionine | 0.6 ± 0.1 | 0.5 ± 0.1 | 0.9 ± 0.1 | 0.4 ± 0.1* | 56.6 ± 1.5 | 49.0 ± 2.4* |
| Phenylalanine | 1.3 ± 0.1 | 1.0 ± 0.3 | 1.7 ± 0.2 | 1.2 ± 0.2 | 109.8 ± 38.5 | 94.6 ± 17.4 |
| Threonine | 5.6 ± 1.4 | 4.4 ± 2.0 | 7.6 ± 0.8 | 4.0 ± 1.2* | 277.5 ± 15.6 | 182.5 ± 21.9* |
| Tryptophan | 0.4 ± 0.0 | 0.4 ± 0.1 | 0.4 ± 0.1 | 0.4 ± 0.0 | 60.9 ± 4.5 | 49.4 ± 2.5* |
| Alanine | 5.0 ± 0.7 | 4.1 ± 0.9 | 7.9 ± 1.1 | 4.6 ± 0.7* | 568.3 ± 32.8 | 642.8 ± 34.5 |
| Asparagine | 1.0 ± 0.2 | 0.9 ± 0.3 | 1.6 ± 0.2 | 0.9 ± 0.2* | 74.6 ± 1.5 | 64.4 ± 4.6 |
| Aspartic acid | 1.1 ± 0.2 | 1.2 ± 0.1 | 1.9 ± 0.7 | 1.8 ± 0.8 | 37.9 ± 2.9 | 36.7 ± 4.3 |
| Citrulline | 0.7 ± 0.1 | 0.5 ± 0.1 | 1.4 ± 0.5 | 0.5 ± 0.1# | 45.5 ± 1.5 | 43.5 ± 1.1 |
| Glutamic acid | 0.8 ± 0.2 | 0.7 ± 0.2 | 1.1 ± 0.3 | 0.7 ± 0.1 | 247.3 ± 19.1 | 208.2 ± 49.1 |
| Glutamine | 33.5 ± 8.8 | 32.0 ± 17.3 | 38.6 ± 7.4 | 28.5 ± 12.6 | 623.9 ± 29.4 | 581.9 ± 27.3 |
| Glycine | 4.8 ± 0.2 | 4.8 ± 0.5 | 6.2 ± 1.5 | 4.9 ± 0.5 | 143.7 ± 5.9 | 127.2 ± 10.7 |
| Ornithine | 3.2 ± 0.2 | 3.7 ± 0.5 | 3.9 ± 0.6 | 3.5 ± 0.6 | 58.5 ± 3.7 | 51.3 ± 2.2 |
| Serine | 4.9 ± 1.2 | 5.1 ± 1.9 | 7.5 ± 2.0 | 5.3 ± 1.4 | 169.6 ± 21.6 | 151.9 ± 10.7 |
| Taurine | 0.9 ± 0.0 | 0.6 ± 0.1 | 1.0 ± 0.2 | 0.5 ± 0.1# | 140.7 ± 20.6 | 121.8 ± 15.6 |
| Tyrosine | 1.5 ± 0.1 | 1.4 ± 0.4 | 2.1 ± 0.2 | 2.1 ± 0.5 | 93.6 ± 5.8 | 85.7 ± 2.9 |
Values are expressed as means ± SE. Rats either remained on NP diet or were transitioned to an isocaloric LP diet. Two days following the transition, cerebrospinal fluid (CSF) lysate samples were obtained with microdialysis before and after intake of an isocaloric NP or LP diet, respectively. Average of two samples collected preprandial (−60 to −30 min and −30 to 0 min relative to food intake) and postprandial (0 to 30 min and 30 to 60 min after food intake) are presented. One hour after the test meal animals were euthanized and trunk blood collected to assess plasma amino acid levels. Values for plasma amino acids are given in μM. Amino acids concentrations were measured via fluorometric HPLC.
P < 0.05 and
P < 0.10 compared NP vs. LP at each time point.