n-heptane and n-hexane enhance in a dose-dependent manner insulin binding to erythrocytes and its degradation.

«-heptane has been effectively used to prepare arteficial bilayer membranes. The viscoelastic and/or mechanical properties of the arteficial membranes vary with changes in the lipid/organic solvent ratio (Hianik et al. 1984). Also changes in cell membrane fluidity are known to correlate with the activities of certain membrane-bound enzymes (Yuli et al. 1981; Stubbs and Smith 1984). membrane receptor endocytosis (Elguindi et al. 1985) or hormone receptor binding (Kolena and Ondriaš 1984). In our previous experiments (Hianik et al. 1986) we could observe that small amounts of insulin added to artificial lipid bilayer changed the viscoelastic properties of the latter. Prompted by these results we tried to examine how would insulin binding and degradation in isolated human erythrocytes change following the addition of /7-heptane in vitro, since this solvent can be assumed to affect viscoelastic characteristics of cell membranes in non-arteficial systems as well. Since also «-hexane can be used to prepare model membranes (Montal et al. 1981; Ayala et al. 1985), we tested the effects of both above mentioned aliphatic hydrocarbons in our system. We present herewith the original observation that following the addition of n-heptane or «-hexane in vitro, insulin binding to human erythrocytes became enhanced; this was associated with similar changes in insulin degradation as measured in the extracellular medium. Moreover, the effect of the organic solvents is likely mediated through processes in the membrane.