A radioimmunoassay of serum 16alpha-hydroxypregnenolone with specific antiserum.

A radioimmunoassay for plasma 16alpha-hydroxypregnenolone has been developed using anti-16alpha-hydroxypregnenolone antiserum produced in rabbits immunized with 16 alpha-hydroxypregnenolone-3-succinate-bovine serum albumin. Radioimmunoassay data were processed and analysed for its validity using a four parameter logistic curve fitting routine with use of the IBM call system. The assay system was satisfactory for a routine use. The 16alpha-hydroxypregnenolone concentrations in the umbilical cord blood at term ranged from 223 to 324 ng/ml. Gas liquid chromatographic analysis revealed a similar result, and also the presence of this steroid in the adrenal gland of the human fetus at midtrimester was confirmed. It is speculated that this steroid is secreted from fetal adrenals.