Fig. 5.

Effect of lysophosphatidylserine (LPS) on 27-HC biosynthesis and HMGR activity. A: 27-HC biosynthesis. Four flasks of fibroblasts were incubated overnight in medium A. The cells were then preincubated for 10 min at 37°C in 4 ml PBS with or without 25 μM LPS. Then 10 mg HPCD alone (designated as minus CH) or 18 mg HPCD bearing 0.45 mg cholesterol (designated as plus CH) was added to the flasks for a 7 min incubation at 37°C. The buffer was replaced with 4 ml PBS ± 25 μM LPS and the flasks incubated at 37°C for an additional 1.5 h. 27-HC synthesis was determined in triplicate, a zero-time background of 4.6 ng 27-HC/mg protein subtracted, and the data expressed as means ± SEM relative to the control. A representative experiment. B: HMGR activity. The experiment was as in A except that the final incubation was for 2 h. HMGR activity was determined and data expressed as means ± average deviation relative to controls. One of two similar experiments is shown.