Abstract-Myelin fragments from rat brain stems were treated with butanol water mixtures and binding experiments of 14C-tryptamine to these extracts (i.e. proteolipids) were performed by Sephadex LH20 column chromato graphy. The elution peak of 14C-tryptamine appeared in a boundary between 6:1 and 4:1 chloroform-methanol, together with 19.2 and 7.3% of the total recoveries of protein and lipid phosphorus, respectively. Various compounds were studied to examine their inhibitory effects on the tryptamine binding to these extracts. The results indicated that only tryptamine and 5-methoxytryptamine inhibited the tryptamine binding, but indole analogues and other neurotransmitters had no effect. The kinetic analysis revealed that the tryptamine binding components present in the myelin butanol extracts are composed of saturable and non-saturable components, and the saturable binding components had an apparent Kd of 1.14X10-7 M. As a preliminary study, myelin butanol extracts were separated into a lipid and protein fractions with ice-cold ether treatment, and then the 14C tryptamine binding capacities of both fractions were examined. The results indicated that only the lipid fraction possessed a tryptamine binding capacity and a chromatographic profile similar to the original butanol extracts. Moreover, the heat-treated preparation of myelin extracts also retained the tryptamine binding capacity. All these observations suggest that the myelin butanol extracts have a specific binding capacity for tryptamine, and its binding components may be lipid in nature.

Abstract-To investigate the nature of the tryptamine binding components that originated from myelin butanol extracts (i.e., myelin proteolipids), the lipid mixtures obtained from these extracts were further fractionated by silicic acid column chromatography, and binding assays of 14C-tryptamine to those fractions were carried out by Sephadex LH20 column chromatography. Among several lipid fractions, only the F-C fraction retained the tryptamine binding properties of the original myelin butanol extracts, i.e., binding capacity, chromatographic profile and interaction with indoleamine analogues and other neurotransmitters. Since the quantitative TLC analysis indicated that this fraction contained a considerable amount of phosphatidylserine (PS) and phosphatidylinositol (PI), recombination experiments with these two acidic lipids were planned. The re combination system with PI did not show a tryptamine binding capacity, while the PS fraction possessed a tryptamine binding capacity similar to that of the myelin butanol extracts. However, displacement studies revealed that the recombinant fraction with PS alone did not display the complete regeneration of the specificity which had been observed in the myelin extracts. All these observations infer that the tryptamine binding components from myelin proteolipids are lipid in nature, and its binding entity is mainly PS. However, some specifically organized constitution with PS and other lipid mole cule(s) may be necessary to regenerate the original tryptamine binding properties.

No abstract

No abstract