Abstract
Summary
In this study paired values of cellular sterol and phospholipid were determined after L cells were grown in medium known to induce changes in the level and kinds of cellular sterol. The sterol to phospholipid molar ratios computed from the paired values showed differences because, while the level of cellular sterol changed in response to exogenous sterol, no statistically significant differences in the levels of cellular phospholipid were apparent.
When L cells were grown in the presence of concentrations of exogenous cholesterol ranging from 0 to 40 μug/ml, the sterol to phospholipid molar ratio ranged from 0.21 ± 0.01 to 0.33 ± 0.04, and, although the cellular sterol ranged from a low level almost exclusively of desmosterol (97%) to a 60% higher level almost exclusively of cholesterol (91%), no statistically significant differences were observed in the amount of cellular phospholipid. In another instance of growth in lipid-free medium a sterol to phospholipid molar ratio as low as 0.16 ± 0.03 was observed. In cell fractions enriched for surface membrane material, sterol to phospholipid molar ratios of 0.27 ± 0.02 and 0.47 ± 0.04 were observed for cells grown respectively in lipid-free and 7.5% serum supplemented medium. Additional analysis by thin-layer chromatography of the total lipid extract showed no apparent differences in the relative amounts of phospholipid classes.
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