Total and Non-Bound Tryptophan in Unipolar Illness

Plasma tryptophan binding to albumin in unipolar depressives

“…Clearly, this is much greater than the change in [A] that we observed, which would only predict a small change of about 5 % in the free tryptophan concentration. This would probably be undetectable in measurements of free tryptophan, consistent with our previous observations ( Riley & Shaw (1976)). It may be that comparisons between the data reported here and those of Coppen & Wood (1978) should take into account both the considerable differences in methods used and the mean ages of the groups.…”

“…Our estimates of the tryptophadalbumin binding constants were in reasonable agreement with the literature values, which confirmed the validity of the method used. These investigations have confirmed our earlier h d i n g (Riley & Shaw (1976)) that there was no major abnormality in the binding of tryptophan to plasma protein in unipolar affective illness. There was no trend in the data to suggest that certain groups of patients selected by age or sex might have significantly abnormal binding characteristics.…”

“…They did not determine control values but the free tryptophan levels reported were similar to the control values reported by Coppen et al (1973). We were also unable to demonstrate any abnormalities in free tryptophan levels in either male or female patients ( Riley & Shaw (1976) M#ller et al (1979) found no difference in non-protein bound and total protein in female depressives, whether they were drug-free or on lithium, unipolar or bipolar, recovered or resistant.…”

“…Tryptophan is unique among the a-amino acids circulating in plasma in that it is partially and reversibly bound to plasma albumin (McMenamy & Oncley (1958)). This binding, which reduces the freely available fraction in human plasma to about 20 % of the total ( Riley & Shaw (1976)), is affected among other things by non-esterifid fatty acids (NEFA). It has been shown in animal experiments that changes in the NEFA level in rat plasma can alter the free tryptophan level without affecting the total tryptophan (Curzon et al (1973)).…”

Depression in Patients With Epilepsy

“…In contrast, other authors (Niskanen et al 1976;Riley and Shaw 1976) were unable to find such changes in plasma tryptophan in depression, although the last group (Riley and Shaw 1976) found that the group of unipolar patients who did not respond to TCAs had significantly lowered total plasma tryptophan. Coppen et al (1972b) reported lowered CSF tryptophan in depressives, but this was not confirmed…”