Improvement in the assessment of human epididymal function by the use of inhibitors in the assay of alpha-glucosidase in seminal plasma.

Seminal alpha-glucosidase has been used clinically as a marker of epididymal function. In this study enzyme inhibitors were used to increase the specificity of the human seminal alpha-glucosidase assay and improve its diagnostic value as an indicator of distal epididymal occlusion in cases of azoospermia. Sodium dodecylsulphate was added to the sample to eliminate the interfering acid isoenzyme secreted by the prostate gland, and castanospermine was used with semen pools to provide a semen blank for the assay by eliminating non-glucosidase-regulated degradation of the substrate. With both inhibitors included in the assay, glucosidase activity in semen samples from 17 fathers was measured to provide reference values for the clinic (lower threshold 18 mU per ejaculate). With the improved assay glucosidase was non-detectable in 8 out of 11 cases of proven and 5 out of 8 cases of suspected ductal obstruction; other azoospermic patients with distal occlusion had values below 11 mU per ejaculate.