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Effect of Choline Deficiency on Utilization of Labeled Precursors of Choline and Turnover of Choline in the Liver of Mature Japanese Quail¹

Department of Animal Sciences, Washington State University, Pullman, Washington 99163

Studies were conducted to determine the effect of choline deficiency on utilization of various labeled precursors of choline and rate of choline biosynthesis in mature Japanese quail. A deficiency of dietary choline did not change the in vivo incorporation of ¹⁴C-label from [1,2-¹⁴C]ethanolamine, N,N-dimethyl[1,2-¹⁴C]ethanolamine, and L-[methyl-¹⁴C]methionine into liver phosphatidylcholine (PC) or total phospholipids. Incorporation of radioactivity from [¹⁴C]serine into liver PC was increased, but the difference was not significant (P > 0.05). In vitro studies confirmed these observations as there were no differences in liver microsomal methyltransferase activities, expressed as the incorporation of methyl-¹⁴C from labeled S-adenosylmethionine into microsomal PC from quail fed a purified diet with or without choline. Rats appeared to incorporate an increased amount of ¹⁴C into PC when fed a diet devoid of choline, but the differences were not significant. There were differences in methyltransferase activities among species, and quail had the lowest activity. A slower turnover of choline was found in quail liver (t_1/2 = 7.5 hours) as compared with that of hen liver (t_1/2 = 2.0 hours). The methyltransferase responsible for the first methylation of phosphatidylethanolamine from quail liver appears to differ from most other biosynthetic enzymes in that it occurs in liver and catalyzes the reaction at a slow rate but cannot adapt to exogenous choline supply to meet the requirements for normal bodily functions in quail.

KEY WORDS: • quail • rat • laying hen • choline biosynthesis • choline deficiency • choline turnover time

¹ Scientific paper no. 4271. College of Agriculture Research Center, Washington State University, Pullman, Wash., project 1985.

² Present address: Northwest Lipid Research Center, University of Washington School of Medicine, Seattle, Wash. 98104.

³ Present address: Department of Poultry Science. University of Georgia, Athens, Ga. 30602.

Manuscript received 7 August 1974.