Formation of 1,2,3,4-tetrahydro-?-carboline and methylene-?-phenylethylimine in the developing rat heart

The formation of tetrahydro-?-carboline and methylene-?-phenylethylimine has been identified by TLC, in the rat heart tissue from labelled 5-methyltetrahydrofolate in the presence of trytamine or ?-phenylethylamine. These compounds were produced when formaldehyde, enzymatically formed from 5-MTHF, condensed with the amines. The enzyme involved in both reactions was again methylene tetrahydrofolate reductase, as in the brain. No N-methylated product was detected with either amine. The reactions were linear with protein concentrations up to 0.9 mg and with incubation time for 40 min. The optimal pH range for both reactions was between 5.5 and 6.5. In the developing rat heart, the formation of TH?C was greatest at 3 days (450 pmol/mg protein/h). It dropped to 290 pmol/mg protein/h at 8 days, peaked again at 15 days, and declined to a constant level (230 pmol/mg protein/h), thereafter. The formation of M??EI was also greatest at 3 days (510 pmol/mg protein/h) and dropped to 280 pmol/mg protein/h between 8 and 15 days, peaking again at 22 days (later than TH?C formation did) to 450 pmol/mg protein/h, dropping back to the 15-day level at 44 days, and showing a rising trend by 53 days. No significant difference between males and females was observed. The in vivo formation of these compounds may be feasible since both tryptamine and ??EA are present in the heart tissue. These reactions may be relevant in the physiological regulation of the cardiovascular system.