ascorbic-acid and tryptamine

Tryptamine was degraded by incubation with rat brain homogenate to an unknown product. The reaction was stimulated by the nonionic detergents Triton X-100 and Lubrol PX and less by the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]1-propanesulfonate (CHAPS). The same results were obtained with pig brain and bovine brain. The monoamine oxidase inhibitor pargyline inhibited the reaction strongly, indicating the participation of the enzyme on the reaction. Addition of 17,000 g supernatant from rat brain homogenate increased the formation effectively whereas phospholipids or chloroform/methanol (7:3) extract from the 17,000 g supernatant showed only little or no effect. Chromatographic and electrophoretic properties as well as the chemical reaction of the product with specific reagents suggest that the compound consists of an indole part and an amino acid part. The product could be identified by fast atom bombardment mass spectrometry and by comparison with the synthetic substance (4R)-2-(3-indolylmethyl)-1,3-thiazolidine-4-carboxylic acid. It is formed by the enzymatic oxidation of tryptamine producing indole-3-acetaldehyde which spontaneously cyclizes with free L-cysteine from the tissue. The results suggest that the reaction of biogenic aldehydes with brain macromolecules may proceed via an analogous reaction.

Topics: Acetaldehyde; Aldehydes; Animals; Ascorbic Acid; Brain; Chromatography, High Pressure Liquid; Ethanol; Female; Hydrogen-Ion Concentration; Indoleacetic Acids; Indoles; Liver; Mass Spectrometry; Octoxynol; Pargyline; Phospholipids; Polidocanol; Polyethylene Glycols; Rats; Rats, Inbred Strains; Tryptamines

The influence of prior incubation on [3H]tryptamine binding was investigated in rat brain synaptic plasma membranes. A 55 min preincubation of the membranes at 37 degrees C induced an approx. 2.4-fold increase in the specific binding of [3H]ligand to the subsequently washed preparations and this phenomenon was quite temperature-dependent. On the other hand, the proportion of nonspecific binding sites was significantly decreased by 70% of the original sites within 20 min of the start of preincubation. Pargyline, ascorbic acid, EGTA, metal ions (Ca2+, Mg2+, Na+) and guanine nucleotides, included in the preincubation buffer, were all inactive on the stimulation of [3H]tryptamine binding, while the pretreatment of membranes with glutaraldehyde antagonized the augmentation of this binding. Furthermore, it was revealed that the Scatchard plot of the [3H]tryptamine binding preincubated at 0 degree C conformed to a straight line (KD = 33.1 nM, Bmax = 543 fmoles/mg protein), whereas a curvilinear Scatchard plot was obtained at 37 degrees C preincubation. Nonlinear regression analysis of the latter resulted in apparent KD (nM) & Bmax (fmoles/mg protein) values of 0.45 & 102.7 and 33.7 & 603.4 for the high and low affinity sites, respectively. All these observations lead to the inference that the preincubation-induced increase in [3H]tryptamine binding (i.e., nearly high affinity proportion of sites) may occur as a result of temperature-sensitive interconvertible conformational changes.

Topics: Animals; Ascorbic Acid; Brain; Cations; Glutaral; Kinetics; Magnesium; Male; Pargyline; Rats; Rats, Inbred Strains; Receptors, Serotonin; Synaptic Membranes; Temperature; Tryptamines

The metabolic significance of indole-3-acetaldehyde in the process of in vitro pigment formation from tryptamine in the presence of guinea-pig liver mitochondria was investigated. Among the four type selective MAO inhibitors used, pargyline and deprenyl appear to be more effective in inhibiting pigment formation from tryptamine than serotonin, while in the presence of clorgyline and Lilly 51641, pigment formation from serotonin was preferentially inhibited. Reducing agents like ascorbic acid, cysteine and glutathione were found to block pigment formation significantly. Also, a reduction of pigment formation was noted in the presence of NADH and ethanol but not in the presence of NAD. It was observed that the amount of indole-3-acetaldehyde produced enzymatically from tryptamine under the present experimental conditions is not sufficient to account for the total amount of pigment formed in the standard incubation mixture and the generation of nascent aldehyde has greater contribution in pigment formation than that supplemented to the system exogenously. It appears that indole-3-acetaldehyde, tryptamine and MAO are associated with the process of pigment formation.

Topics: Animals; Ascorbic Acid; Glutathione; Guinea Pigs; In Vitro Techniques; Indoles; Mitochondria, Liver; Monoamine Oxidase; Monoamine Oxidase Inhibitors; Pigments, Biological; Tryptamines