Oxidation in vivo of the methyl groups of choline, betaine, dimethylthetin, and dimethyl-beta-propiothetin.

It has recently been demonstrated in this laboratory (l-3) that “biologically labile” methyl groups can be oxidized to CO2 in the rat. This has been established by feeding methionine containing radioactive carbon in the methyl group and demonstrating the presence of radioactive CO2 in the expired air. In the present communication a comparison is made of the rates of oxidation of methyl groups administered ss choline, betaine, dimethylthetin (4), and dimethyl-&propiothetin (5). These compounds, labeled with Cl4 in one methyl group, have been prepared and injected intraperitoneally into rats. The radioactivity of the CO2 in the expired air was measured at intervals during a 24 hour period.