Table 3. No preferential insertion of C₆-SM into lipid rafts.

Lipid	Total	DRM	non-DRM
Endogenous SM	13.15±3.96	11.86±1.26	2.87±0.34
Inserted C6-SM	1.81±0.47	0.22±0.17	1.16±0.56

BAEC were incubated for 60 min with 10 μM C₆-SM. DRM were then isolated by solubilisation of the cells in ice-cold Triton X-100, and a subsequent ultracentrifuge run on a discontinuous sucrose gradient (see Materials and Methods). The initial Triton X-100 suspension was designated as total. The upper half of the gradient was designated as DRM, and the lower half as non-DRM. Total lipids were extracted from all three samples and glycerol-containing lipids were removed by a mild alkaline hydrolysis procedure. The remaining lipids were then separated by TLC and visualised by iodine vapour staining. C₆-SM and endogenous SM containing spots were scraped from the plate and subjected to a colorimetric phosphate determination. Lipid contents are expressed as nmol mg⁻¹ of total cellular protein (±s.d., n=3).