BUTANOL EXTRACTS FROM MYELIN FRAGMENTS: SOME CHARACTERISTICS OF TRYPTAMINE BINDING

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 LH2O column chromatography. 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 1.14x 10−7 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.