FIGURE 3.

The regulation of phospholipid synthesis for a short time does not affect the levels of [³H]PC, [³H]PI, or [¹⁴C]TAG. CHO-K1 and CHO-MT58 cells were labeled with [³H]choline (A), [³H]inositol (B), or [¹⁴C]acetate (C) for 24 h. Cells were then washed and incubated for 1 h in HEPES buffer with 200 μm choline and 5 mm inositol (+s), without these substrates in the presence of 5 mm LiCl (−s), or with F-12 (Ham's) growth medium (F12) at the temperature indicated (33 or 40 °C). Samples at the starting point of the assay (to) were also monitored. Lipids were extracted, separated by TLC, and counted for radioactivity. Results are mean ± S.D. (error bars) of two experiments performed in triplicate (A and B) or duplicate (C).