[Studies on gamma-glutamyl transpeptidase (gamma-GTP) in seminal plasma]

The significance of gamma-GTP (gamma-glutamyl transpeptidase) in seminal plasma was examined by measuring the gamma-GTP activity in ejaculate, seminal plasma, prostatic secretion, testis, epididymis, vas deferens, prostate and sperm. The gamma-GTP activity was measured spectrophotometrically (405 nm) using L-gamma-glutamyl-p-nitroanilide as a substrate. One unit of enzyme activity was defined as the amount liberating 1 mumol of p-nitroaniline per min. The mean gamma-GTP activity was 9,094 +/- 4,351 mU/ml in ejaculate and 7,487 +/- 4,286 mU/ml in seminal plasma of 76 men visiting the infertility clinic. There is a positive correlation between gamma-GTP activity in ejaculate and in seminal plasma. The gamma-GTP activity was 15,044 +/- 6,422 mU/ml in prostatic secretion and twice as high as the activity in seminal plasma. There was no significant correlation between gamma-GTP activity in seminal plasma and volume of ejaculate, sperm density or sperm motility. The gamma-GTP activity in testicular tissues was 72 +/- 25 mU/mg protein except for two cases in which its activity was not detected (3 years old; retentio testis, 71 years old; prostatic carcinoma, was administered with hormonal medicine). The gamma-GTP activity in prostatic tissues was 133 +/- 68 mU/mg protein. The relationship between the gamma-GTP activity in testicular tissues and Johnsen's mean score count. Judging from the present results together with the previous reports of Rosalki et al (1977) and Simon et al (1978) the prostate seemed to be the major source of gamma-GTP in human semen.