Values of amino acid concentrations measured in blood plasma, CSF and ISF are summarized in Table 3. There is agreement in all studies that, with the exception of glutamine, the concentrations of all other amino acids in CSF and ISF are substantially less than those in plasma. This could arise if the rates of consumption were to reduce the concentrations greatly or if there were active transport of amino acids from brain fluids to blood. Whether or not there is a substantial difference in amino acid concentrations between CSF and ISF is less clear.17
Table 3 Amino acid concentrations in plasma, CSF and ISF
Plasma concentration/µM CSF concentration/µM ISF concentration/µM
Human1 Rat2 Human3 Rabbit4 Rat5 Mice6 Human1 Human7 Rat2, c Rat1, 2 Human3 Rabbit4 Rat5 Mice6 Rabbit4 Rabbit8 Rabbit9 Rat5 Mice6
Gln 619 641 868 834 598 863 780 552 583 524 517 250 547 159 193 80
Asn 112 55 Trace 14 16 3 7.8 4.3 1.4
Ala 330 489a 382 430 408 27 18.6 34a 39 85.4 57 15 19 15 7.7 9.3
Ser 149 196 140 263 247 109 28.9 30.4 79 80 30 116 62.3 37 34 24.9 9.8
Gly 249 221 283 246 1.3 6.4 20 15 6 34 7.8
Pro 212 60 Trace 0.6 4.2 1.8
Thr 142 166 113 28.5 27.7 36 22 3.5
Val 222 430 309 191 173 14 16.1 78 47 20 14 9.4 13 12.5 7.4 2.9
Leu 109 432 155 81 127 13.1 11.9 66 42 15 7 6.6 9 1.5
Ile 61 77 101 5.2 4.7 6 7 9
Tyr 70 73 43 54 7.3 8.1 10 7 7.2 5 0.7
His 85 80 59 10.8 12.0 12 8.9 1.2
Lys 158 290 171 137 321 19.7 22.0 120 87 21 8 46 19 10
Arg 80 94 81 227 103 17 18.6 55 46 22 32.5 18 6.9 3.2
Glu 83 61 56 159.6 37 7.2 8.7 26 10 11.4 21 4 4.3 3.4 2.9 4.1
Asp 7 33.8 2.4 1.5 5.8 0.6 0.5 1.7
Phe 71 64 45 8.3 8.2 10 7 6
Met 41 28 30 2.8 2.6 3 3
Trp 62
Concentrations measured in CSF are, with the exception of glutamine always substantially less, than the concentrations in plasma. Concentrations in ISF are measured by microdialysis with extrapolation to zero flow (see text). If these are correct, ISF concentrations are substantially lower than those in CSF. c cisternal, l lumbar
1Plum et al. [576]
2Franklin et al. [577]
3McGale et al. [578]
4Hamberger et al. [579]
5Lerma et al. [580]
6Dolgodilina et al. [581]
7Table 8.15 in Davson and Segal [56]
8Jacobson et al. [582] microdialysis by concentration profile
9Jacobson et al. [582] microdialysis by recovery of samples