Specificity of hemolymph proteins for cholesterol binding in Periplaneta americana L.

In the present investigation, specificity of hemolymph proteins for the binding of cholesterol, cholesterol acetate and two of the major plant sterols, sitosterol and stigmasterol was studied by subjecting the prelabelled hemolymph of P. americana to gel filtration chromatography. The hemolymph proteins showed high affinity and low capacity for cholesterol and cholesterol acetate but low affinity and high capacity for sitosterol and stigmasterol. The maximum binding was that of cholesterol followed by cholesterol acetate, sitosterol and stigmasterol in a decreasing order. The binding of a labelled sterol in the presence of other sterol at higher concentration was also studied. The binding of cholesterol was reduced from 78% to about 40% in the presence of sitosterol or stigmasterol and to 22% in the presence of cholesterol acetate. Cholesterol acetate and sitosterol binding to hemolymph proteins was also reduced in the presence of other sterols in hemolymph, whereas the percentage binding of stigmasterol increased in the presence of other sterols.