The assay of cholesterol sulfate in biological material by enzymatic radioisotopic displacement

A technique is described for the measurement of cholesterol sulfate (CS) which is based upon the displacement of labelled CS from a placental sulfatase enzyme system by the addition of unlabelled CS isolated from various biological sources.From the extent of this displacement by unknown samples of CS and by reference to standard curves, the concentration of CS in the biological samples can be calculated. This assay method is relatively simple, rapid, and sensitive (nanogram level) and provides values which are in good agreement with those obtained by a double isotope derivative assay. Levels of CS in human plasma, erythrocytes, semen, and saliva have been determined. This sterol sulfate appears to be a ubiquitous entity although its biological function remains to be determined. Certain aspects of its possible physiological role in the organism are discussed.