Plasma tyrosine/neutral amino acid ratio correlated with clinical response to nortriptyline in endogenously depressed patients

A Multivariate Analysis of Red Blood Cell Membrane Transports and Plasma Levels of <i>L</i>-Tyrosine and <i>L</i>-Tryptophan in Depressed Patients before Treatment and after Clinical Improvement

“…Earlier studies about plasma TYR, PHE and TRP have so far yielded inconsistent findings [Niskanen et al, 1975;de Myer et al, 1981;Joseph et al, 1984;Möller et al, 1985;Maes et al, 1987;Bovier et al, 1988;Mathis et al, 1988]. But some authors point out the possible role of membrane transport phenomena as regulatory activity in general homeostasis processes by establishment of flows in direction just as in magnitude [Christensen, 1986].…”

“…It must also be acknowledged that many previous investigations con cerning plasma levels of different amino acids in the field of depression have until now yielded inconsistent findings [Niskanen et al, 1976;De Myer et al. 1981;Möller et al, 1985;Maes et al, 1987], However, this question should be carefully formulated in a context of complexity each parameter 'per se' gets intrinsic proper ties but is also integrated in a functional system which confers on its 'elementary' properties. It is difficult to delete such an essential process.…”

Positron Emission Tomography Measurement of Cerebral Metabolic Correlates of Tryptophan Depletion—Induced Depressive Relapse

“…[15,16] Plasma L-tryptophan competes with other competing amino acids (CAAs) for uptake into the brain and is affected by factors that influence L-tryptophan plasma protein binding, such as levels of albumin or insulin. [17] Some studies, [18,19] but not others, [20][21][22] found a decrease in plasma tryptophan, or the ratio of tryptophan to CAAs in some studies, [18,[23][24][25][26] but not in others, [20,27] in patients with major depression. Lower tryptophan availability was related to specific depressive symptoms (but not core depressive symptoms), [28] and it predicted treatment response to amitriptyline in some studies, [23] but not in others.…”

In vitro Effects of lonophores and Inhibitors of Main Sodium and Calcium Movements on Tyrosine and Tryptophan Transport by Human Erythrocytes

“…Norepinephrine, dopamine and serotonin, as well as their precursors, the amino acids tyrosine (TYR) and tryptophan (TRP), have been implicated in theories on the mechanisms of psychiatric disorders [Tissot et al, 1978;Candace et al, 1983;Möller et al, 1983Möller et al, , 1985, Since direct study of brain biochemistry is impossible in man, an alternative is to use peripheral models such as platelets, lymphocytes or erythrocytes. These peripheral indices might be specific markers in various psychiatric conditions [Widmer et al, 1982;Rotman, 1983;Siever and Coursey, 1985;Widmer et al, 1985], TYR and TRP are carried across the membrane of human red blood cells by the L (TYR) and T (TRP) transport systems.…”