Phosphatide turnover studies

Further evidence in support of the decreased rate of phosphatide turnover in choline deficiency is provided by studies (27) in which choline containing was fed to both normal and choline-deficient animals. Incorporation of new choline (tagged by the presence of was found to be retarded in the choline-deficient rat. 

The expected incorporation of mi/o-inositol into phospholipids has been observed in two31 126 and in kidney preparations in vitro,138 and some progress has been made toward understanding the enzymic mechanism involved.101 1 138,139 It appears that the inositol is neither phosphorylated nor converted to a coenzyme prior to incorporation. Hokin and Hokin140 have made the interesting observation that the turnover of myo-inositol in the monophosphoinositide of brain and pancreas slices is stimulated by acetylcholine. The effects of various drugs on this turnover have been studied by other workers. It has been postulated that the decomposition and resynthesis of inositol phosphatide is a part of the membrane-transport process.140... 

The knowledge of exact turnover figures is of interest when comparing, for example, the amount of fat metabolized with the amount of phospha-tides turned over. In many cases however we can draw conclusions merely by comparing the specific activity of the phosphatides present in an organ under varying conditions. Such a procedure is applied in the study of the effect of ingested fat on the rate of renewal of phosphatides, of the effect of choline, cholesterol, and other substances on the turnover of liver phosphatides, of the site of fonnation of the yolk, embryo, and milk phosphatides, and so on. 

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