Assay for free and total choline activity in biological fluids and tissues of rats and man with Torulopsis pintolopessi.

The sensitive, specific growth response to choline activity of the thermophilic enteric yeast Torulopsis pintolopessi enables estimation of free and bound choline activity in rat and human fluids and tissues- as little as 10 ng/ml of choline is measurable. Unlike other microbial assays, estimation of unbound (free) choline activity is not influenced by methionine or phospholipids. The method also distinguishes differences in choline activity of fluids and tissues from choline-deficient and choline-replete rats. Free and bound choline activity in blood, red blood cells, plasma, and liver from choline-deficient rats were almost 2-fold lower than from choline-supplemented animals. Free and bound choline activity in whole brain from choline-deficient rats were signifigantly higher (more than 2-fold). The application of the T. pintolopessi method in studying choline status in man and reasons for high choline activity in brain of choline-deficient rats are suggested.