Ascorbate-induced lipid peroxidation and the binding of [3H]dihydroalprenolol

Sodium ascorbate addition caused a modest loss in the specific binding of [3H]dihydroalprenolol ([3H]DHA) in a rat cortical membrane preparation. Sodium ascorbate also caused a modest increase in lipid peroxide formation in the membrane preparation. Both the lipid peroxidation and the loss in [3H]DHA binding were greatly potentiated by the addition of low levels of iron (Fe2+). A kinetic analysis indicated that the iron/ascorbate caused a loss in the number of [3H]DHA binding sites but had no effect on the affinity of [3H]DHA for the binding site. Both the lipid peroxidation and the loss of [3H]DHA binding were prevented by iron chelating agents (e.g. EDTA) and by classical inhibitors of lipid peroxidation (e.g. propyl gallate, cobalt chloride). All of these data taken together suggest that an iron-dependent lipid peroxidation results in a loss of [3H]DHA binding sites. These and other data further suggest that lipid is critical for the binding of [3H]DHA to its receptor.