Steroid sulphatase activity in the skin biopsies of various types of ichthyosis.

A simple method was developed for the determination of steroid sulphatase activity in a skin biopsy for routine use. In this method, 6 mg of minced tissue is incubated in 1 ml of Krebs-Ringer bicarbonate buffer with radioactive dehydroepiandrosterone sulphate (20,000 c.p.m., S.A. 1.1 Ci/mmol) for 4 h. After the incubation the liberated unconjugated dehydroepiandrosterone and its possible metabolites are separated from the conjugated compound by extraction with ethyl acetate-ethyl ether 10:90 (v/v). The organic phase is counted in a scintillation counter. The results are expressed as c.p.m. values per 6 mg tissue wet weight. Steroid sulphatase activity was measured in skin biopsies from nine control subjects and from thirteen patients with various types of ichthyosis. In the different groups studied, the ranges of the c.p.m. values were as follows: controls (n = 9) 377-1802; X-linked ichthyosis (n = 5) 140-214; ichthyosis vulgaris (n = 5) 607-1320; ichthyosiform erythroderma (n = 2) 2146-2214; lamellar ichthyosis (n = 1) 2185. The reagent blank varied from 180 to 259 c.p.m. In X-linked ichthyosis the c.p.m. values were always less than in the corresponding reagent blank, indicating that no enzyme activity was present in the tissue. In other types of ichthyosis, steroid sulphatase activity was normal. The method described is easy to accomplish in any clinical laboratory where scintillation counting is possible.