Plasma Total and Free Tryptophan Concentration in �Neurotic� and �Psychotic� Depressive Patients1

Models of tryptophan catabolism and binding to serum albumin are presented to explain the observed effect of displacement of tryptophan from albumin on the concentrations of free and bound tryptophan and on the rate of 5-hydroxytryptamine (5-HT) synthesis from tryptophan in the brain. A rapid rate of dissociation of tryptophan from albumin (compared to the transit time of tryptophan through the liver) and a large fractional extraction of the free pool of tryptophan during passage through the liver are shown to be necessary factors in determining the effects observed. Because of the low fractional extraction of free tryptophan in the brain, the synthesis of 5-HT will be dependent only upon the free pool of tryptophan. Dissociation of tryptophan from albumin only causes a sustained increase in 5-HT synthesis in the brain because of the effect that this dissociation has on hepatic tryptophan catabolism and thereby on the free pool of tryptophan.

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TOTAL AND FREE TRYPTOPHAN CONCENTRATION IN THE PLASMA OF DEPRESSIVE PATIENTS

The Lancet ◽

10.1016/s0140-6736(72)92980-7 ◽

1972 ◽

Vol 300 (7792) ◽

pp. 1415-1416 ◽

Cited By ~ 32

Author(s):

A Coppen ◽

E.G Eccleston ◽

M Peet

Keyword(s):

Free Tryptophan ◽

Tryptophan Concentration ◽

Depressive Patients

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TOTAL AND FREE TRYPTOPHAN CONCENTRATION IN THE PLASMA OF DEPRESSIVE PATIENTS

The Lancet ◽

10.1016/s0140-6736(73)93259-5 ◽

1973 ◽

Vol 302 (7820) ◽

pp. 60-63 ◽

Cited By ~ 113

Author(s):

A. Coppen ◽

E.G. Eccleston ◽

M. Peet

Keyword(s):

Free Tryptophan ◽

Tryptophan Concentration ◽

Depressive Patients

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Plasma Free Tryptophan Concentration in Children with Attention Deficit Disorder

Psychiatry and Clinical Neurosciences ◽

10.1111/j.1440-1819.1985.tb00807.x ◽

1985 ◽

Vol 39 (4) ◽

pp. 531-535

Author(s):

Yoshihiko Hoshino ◽

Yoshinori Ohno ◽

Toshiaki Yamamoto ◽

Motohisa Kaneko ◽

Hisashi Kumashiro

Keyword(s):

Attention Deficit ◽

Attention Deficit Disorder ◽

Free Tryptophan ◽

Tryptophan Concentration

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The effects of diet, lipolysis and limb ischaemia on the distribution of plasma tryptophan in the rat

Biochemical Journal ◽

10.1042/bj1460659 ◽

1975 ◽

Vol 146 (3) ◽

pp. 659-666 ◽

Cited By ~ 10

Author(s):

H B Stoner ◽

V J Cunningham ◽

P M Elson ◽

A Hunt

Keyword(s):

Fatty Acid ◽

Acid Concentration ◽

Fatty Acid Concentration ◽

Limb Ischaemia ◽

Plasma Tryptophan ◽

Free Tryptophan ◽

Esterified Fatty Acids ◽

Tryptophan Concentration ◽

Free Plasma ◽

Sustained Increase

A non-linear relationship between the plasma non-esterified fatty acid concentration and the percentage of free plasma tryptophan was found in rats in different nutritional states, although non-esterified fatty acids are not the only factors determining the percentage of free tryptophan. This relationship was not seen in rats injured by limb ischaemia. The effect of drugs causing rapid increases in the plasma non-esterified fatty acid concentration was also studied. Isoprenaline decreased the total plasma tryptophan concentration. Dichloroisoprenaline caused a sustained increase in the plasma non-esterified fatty acid concentration which was accompanied by an increase in the concentration of free plasma tryptophan and followed by a fall in the concentration of total tryptophan. The loss of tryptophan from the plasma was attributed to an altered distribution of tryptophan in the extracellular space rather than to increased metabolism. This interpretation was supported by determinations of the irreversible disposal rate of plasma tryptophan which in uninjured rats was unaffected by the concentration of free plasma tryptophan. In the injured rats this rate was unaltered during limb ischaemia but was decreased after removal of the tourniquets; increased competition for tissue entry by other neutral amino acids and the fall in body temperature could be factors in this fall.

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