The possible meaning of transferrin and its soluble receptors in seminal plasma as markers of the seminiferous epithelium

Transferrin (Tf) and soluble transferrin receptors (S-Tf-R)were measured by enzyme immunoassay in seminal plasma of 130semen samples. The mean concentration of S-Tf-R in cases withnormozoospermia was 10.4 IU/ml (95% confidence interval: 9.5–11.3)and it was significantly lower in patients with oligozoospermia(6.6, 95% CI: 5.8–7.5, P < 0.001), asthenozoospermia(8.5, 95% CI: 5.5–10.7, P < 0.05), azoospermia of primarytesticular origin (7.9, 95% CI: 6.1–9.6, P < 0.05)and post-vasectomy samples (5.9, 95% CI: 5.4–6.9, P<0.001). The concentration of S-Tf-R in post-vasectomy sampleswas lower than that in patients with azoospermia of primarytesticular origin (P< 0.05; positive likelihood ratio= 7at value of 8.3 IU/ml). S-Tf-R was positively correlated withmotile sperm concentration (r= 0.50, P< 0.0001), percentagemotility (r= 0.38, P< 0.001), percentage of normal forms(r = 0.43, P < 0.001), sperm linear velocity (r= 0.42, P<0.001), and ATP concentration (r= 0.67, P< 0.0001). Folliclestimulating hormone (FSH) was found to be negatively correlatedwith the concentrations of both Tf (r= -0.31, P< 0.05) andof S-Tf-R (r= -0.45, P< 0.01). The mean concentration ofTf in seminal plasma was 50.4 µg/ml (35.9–67.2)in samples with normozoospermia (n= 22), and the concentrationwas significantly lower in patients with oligozoospermia (P<0.05), azoospermia of testicular origin (P < 0.001), andpost-vasectomy samples (P< 0.001). Seminal Tf was correlatedwith motile sperm concentration (r = 0.36, P< 0.001), percentageof motile spermatozoa (r= 0.25, P < 0.05), linear velocity(r= 0.24, P< 0.05) and ATP concentration (r= 0.44, P<0.001). The concentration of Tf was positively correlated withthat of S-Tf-R both in cases with spermatozoa present (r= 0.66,P < 0.001), and in cases with azoospermia of testicular origin(r = 0.51, P < 0.05) but not in vasectomy cases. It is concludedthat S-Tf-R in seminal plasma is a marker of spermatogenesisand may give information on the presence or absence of spermatogeneticcells in cases with azoospermia. Further investigations areneeded to assess its usefulness for clinical practice.