Incorporation of [15N]-ethanolamine and [15N]-choline into phospholipids in various organ tissues of young and adult mice after the intraperitoneal injection.

Incorporation of [15N]-ethanolamine into phospholipids in various organ tissues of 12-days-old and adult mice was investigated in the time course after the intraperitoneal injection. The incorporation of [15N]-choline into phosphatidylcholine was also investigated only in adult mice. Concentration of 15N-atom% excess in different phospholipids was determined by optical emission spectroscopic 15N-analyser. It was found that the incorporation of [15N]-ethanolamine into phosphatidylethanolamine gave different rates in various organ tissues. The [15N]-phosphatidylethanolamine was converted into [15N]-phosphatidylcholine only in liver which gave the highest incorporation rate of [15]-ethanolamine into phosphatidylethanolamine. The rates of transmethylation of phosphatidylethanolamine into phosphatidylcholine were estimated and found to be much higher in young mice than in adult, even if the time lag in the transmethylation was observed in young mice. Also, it was noted that [15N]-choline was actively incorporated into phosphatidylcholine specifically in liver, but hardly in the extrahepatic organ tissues. The phosphatidylcholine synthesized in liver seemed to be rather transferred directly to the extrahepatic organ tissues.