The nitrogenous constituents of the lipids of several dog tissues.

A technique is described for the resolution and quantitative determination of the nitrogenous constituents of dog tissue lipids. Results of representative analyses are presented for seven different tissues. All but a few per cent of the total lipid nitrogen has been specifically accounted for as choline, ethanolamine, serine, other amino acids, ammonia, sphingosine, and hexosamine. Serine-containing lipids comprise a maximum of 2.6% to 7.7% of total lipid nitrogen of the tissues studied. Despite extensive purification of the lipid extracts, other amino acids and peptides are present in quantities comparable to serine. The ammonia content of the lipid hydrolyzates ranges from 4.3% to 5.9% of lipid nitrogen. From 1.0% to 9.4% of lipid nitrogen becomes water soluble after hydrolysis, and is neither choline, ammonia, nor primary amine. This is considered to be substituted amine, although no important fraction of this material has been identified.