Quantitative Determination of the Binding Capacity of the Sex Hormone-Binding Globulin, Using Agar Gel Electrophoresis

Abstract

An easy, rapid and precise technique for determining the binding capacity of sex hormone-binding globulin (SHBG) was described. The plasma was incubated with [3H]5-.alpha.-dihydrotestosterone (DHT) alone, or together with an excess of unlabeled DHT. The SHBG-binding peaks were demonstrated by agar gel electrophoresis according to Wagner, and the SHBG-binding capacity was calculated from the radioactivity specificially bound to the SHBG peak, corrected for the dissociation of the [3H]DHT from SHBG during the 90-min electrophoresis. In addition to investigating various problems of methodology, the following clinical results were obtained: normal range (mean .+-. SD) of the SHBG-binding capacity for males (age 22-41; n = 26) was 38 .+-. 11 nM. An older male group had, with 48 .+-. 10 nM, a significantly higher binding capacity. The highest values found so far were in pregnancy plasma of the 3rd trimester (330 and 400 nM).