ACID CATALYSIS OF THE FORMALDEHYDE CONDENSATION REACTION FOR SENSITIVE HISTOCHEMICAL DEMONSTRATION OF TRYPTAMINES AND 3-METHOXYLATED PHENYLETHYLAMINES : 1. MODEL EXPERIMENTS
1 Institute of Anatomy and Histology, University of Lund, Lund, Sweden
Hydrochloric acid catalyzes the formation of fluorophores in the histochemical condensation reaction between gaseous formaldehyde and certain phenylethylamines and indolylethylamines. Thus, when the formaldehyde reaction is carried out in the presence of minute amounts of HCl gas, 3-methoxy-4-hydroxyphenylethylamine, 3,4-dimethoxyphenylalanine and tryptamine displayed a fluorescence yield approximately 20-200 times higher than that obtained after standard formaldehyde treatment in normal air (i.e., the conditions of the Falck-Hillarp method). This fluorescence intensity was nearly twice as high as that obtained from noradrenaline and dopamine under the standard conditions. The results indicate that the acid catalyzes the first step of the histochemical reaction, i.e., the Pictet-Spengler condensation reaction. In this step low fluorescent tetrahydroisoquinolines and tetrahydro-
|
|
||||||||||||