[Studies on the source of androgen binding protein (ABP) in human seminal plasma (author's transl)]

Androgen binding protein in human seminal plasma (SPABP) which has a high affinity-low capacity for dihydrotestosterone (DHT) was measured by saturation-charcoal adsorption technique. No correlation was found between SPABP binding capacity for DHT and sperm count or motility, but there was a significant correlation between SPABP binding capacity per ejaculate and semen volume. In order to determine the source of this binding protein seminal plasma from vasectomized men was analyzed, split ejaculates were studied from normal volunteers and SPABP was compared from epididymal ABP and from serum testosterone-estradiol binding (TeBG) by isoelectric analysis. There was no significant difference in SPABP binding capacity in semen from vasectomized (293.2 +/- 84.2pM) and non-vasectomized men with azoospermia (289.6 +/- 108.6pM). Analysis of split ejaculates showed the following: 1) the sperm density was significantly greater in the first fraction; 2) the concentration of fructose was greater in the second fraction; 3) SPABP binding capacity was the same in both fractions. The isoelectric analyses showed that SPABP was distinctly different from epididymal ABP and serum TeBG. In these data, this DHT-binding protein is not the same as testicular ABP. It appears to originate from both the prostate and seminal vesicles.