The effect of sterol structure on the permeability of lipomes to glucose, glycerol and Rb+

Abstract

1. 1. The effect of 3β-, 3α-hydroxysterol and ketosteroids on the permeability properties of (egg lecithin) liposomes towards glucose, glycerol and Rb+ has been studied.

2. 2. The 3β-hydroxysterols, cholesterol, cholestanol, lathosterol, 7-dehydrocholesterol and B-norcholesterol affect the most pronounced reduction in permeability of glucose, glycerol and Rb+.

3. 3. The plant sterols, ergosterol and stigmasterol are less effective whereas compounds lacking the side chain (androstan-3β-ol) or with a non-planar sterol nucleus (coprostanol) show no effect.

4. 4. The 3α-hydroxysterols, epicholesterol and androstan-3α-ol reveal no significant effect on the permeability.

5. 5. The ketosteroids either do not affect the permeability or increase the permeability of the lipid barrier.

6. 6. The reduction in permeability, as found for cholesterol, is dependent on: (a) planar sterol nucleus, (b) 3β-hydroxy group, (c) intact side chain.

7. 7. The effect of sterols on the permeability properties of liposomes are in good agreement with the effect on the mean molecular area measured in monolayers, and the effect of these sterols on biological membranes such as erythrocytes and Mycoplasma.