Studies of the Human Testis. XV. Androgen-Binding Protein and Function of Leydig Cells and Tubules in Aged Men with Prostatic Carcinoma*

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Abstract
Further methodology is presented for the determination of human androgen-binding protein (hABP) in human testis using testis tissue obtained from 14 patients, aged 62–82 yr, undergoing orchiectomy for treatment of prostatic carcinoma. Binding of testosterone-estrogen-binding globulin to Concanavalin A-Sepharose (Con A) during affinity chromatography is used to remove possible contaminating plasma testosterone-estrogen-binding globulin from the hABP fraction of testis used for assay. While large pieces of testis tissue (2–3 g) can be freed of plasma contamination by presoaking, the Con A method is used for biopsy-sized pieces(50–100 mg). Two assay techniques (dextran-coated charcoal and steady state polyacrylamide gel electrophoresis) produce comparable results for [3H]dihydrotestosterone binding affinity and capacity. Using a Kd of 1.2 nM, a single point assay isused to determine the hABP binding capacity in small amounts of testis after Con A treatment. The results are comparable with those obtained using larger amounts of tissue when binding curves are constructed and the data are subjected to Scatchard analysis. The hABP binding capacity ranges from 0.05–0.32 pmol/100mg tissue (mean, 0.14). Astudy of other indexes of testicular function reveals a significant (P < 0.01) positive correlation of hABP with intratesticular testosterone levels and with the number of Leydig cell clusters per tubule. The intratesticular testosterone concentration is also positively correlated with the Leydig cell cluster index. There is no correlation of hABP binding capacity with histological indexes of spermatogenesis or tubular wall changes. The ability to detemine hABP in small amounts of testis provides an approach to further study human testicular function. Additional studies may clarify the significance of the close correlation of hABP and intratesticular testosterone. (J ClinEndocrinol Metab50: 1105, 1980)

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