Measurement of α-glucosidase (α-GLUC) activity by means of a simple colorimetric test using a commercial kit (EpiScreen®; FertiPro, Lotenhulle, Belgium) yielded results that were strongly correlated with the values obtained for the neutral iso-enzyme measured by a fluorimetric reference method (r = 0.85, P = 0.003, n = 13). The former method was characterized by a low intra- and inter-coefficient of variation (6.6 and 4.3% respectively). Vasectomized men with azoospermia (n = 27) had a significantly lower α-GLUC activity in semen than vasectomized men with residual spermatozoa present (n = 11, P < 0.01) and men with azoospermia of primary testicular origin (n = 33, P < 0.01). Receiver operating curve (ROC) analysis showed α-GLUC measurement to be reasonably accurate in differentiation between cases with obstructive versus testicular azoospermia at criterion value 13.5 U/l (sensitivity = 82%, specificity = 70%). In cases with spermatozoa present, α-GLUC activity and output per ejaculate were positively correlated with sperm concentration (r = 0.53 and 0.38, n = 472), linear velocity (r = 0.35 and 0.30, n = 224), curvilinear velocity (r = 0.32 and r = 0.29, n = 224), semen adenosine triphosphate (r = 0.35 and 0.26, n = 64), the concentration of 5α-dihydrotestosterone (r = 0.31 and 0.29, n = 74), and γ-glutamyltransferase activity (r = 0.62 and 0.32, n = 275) in seminal plasma. The activity of α-GLUC was inversely correlated with ROS generation after 12-myristate, 13-acetate phorbol ester stimulation (r = -0.27, n = 104), and both α-GLUC activity and total output were inversely correlated with the concentration of peroxidase-positive white blood cells among samples with ≤ 1 x 106/ml of these cells (r = -0.30 and -0.19, n = 165). It is concluded that simple photometric measurement of α-GLUC activity in seminal plasma reflects the functional state of the epididymis and may be helpful for the differential diagnosis of certain cases with azoospermia.
