LACTATE DEHYDROGENASE AND ITS ISOZYMES IN HUMAN EJACULATE

Abstract

A quantitative study was carried out on the lactate dehydrogenase (LDH) and its isozymes in ejaculates of 170 men, testicular tissues of 12 men and accessory sexual organs of 10 men. LDH activities were assayed on the basis of the rate change of NADH concentration during the convertion of pyruvate to lactate at 37°C by measuring light absorbance at 340nm spectrophotometrically. LDH isozymes were separated by agar-gel electrophoresis. The isozymes were then visualized by incubating the gel in a buffer solution containing blue tetrazolium salts, phenazine methosulfate, NAD and lactate as substrate. The relative proportions of the isozymes were estimated by scanning the stained gel at 570nm in Densitron 1M (Joko & Co.).
The LDH activity of the normospermia (n=16) was 5280±3217mU/ml (mean±S. D.) and the mean % distributions of the enzyme activity among isozymes were 3.9±1.6% for LDH₁, 14.7±3.3% for LDH₂, 24.0±4.3% for LDH₃, 21.6±11.1% for LDHx, 20.9±5.6% for LDH₄ and 14.6±7.3% for LDH₅.
The LDH activity and sperm count revealed significant correlations (n=1; 0, r=0.50, p<0.001). But there was no significant correlation between the enzyme activity and sperm motility. The LDHx was recognized in 96.6% of ejaculates with sperm counts above 50 million/ml, in 100% of those with sperm counts from 20 to 50 million/ml, in 93.5% of those with sperm counts between 20 and 10 million/ml, in 52% of those with sperm counts under 10 million/ml and in 0% of azoospermia.
There appeared to be a tendency that the higher the sperm motility in the ejaculates, the higher the incidence of the presence of LDHx in ejaculate.
Both LDH₁ and LDH₂ showed no relations to sperm counts. While activities of LDH₃ (r=0.38, p<0.01), LDH₄ (r=0.42, p<0.01) and LDH₅ (r=0.27, p<0.01) respectively revealed significant correlations to sperm counts. Especially LDHx activity revealed a high correlation to sperm counts (r=0.60, p<0.01).
The activity of each isozyme including LDHx showed no significant correlation to sperm motility.
After vasectomy, LDHx fraction disappeared from seminal plasma and total LDH activity was significantly reduced to 2901mU/ml from 3838mU/ml (p<0.05).
Six patients with varicocele who had demonstrated oligospermia with lacked LDHx in the ejaculates underwent high ligation of spermatic vein. LDHx was recovered in seminal plasmas of 5 of them with improved sperm counts.
Fresh spermatozoa were washed with physiologic saline 4 times until almost no LDH activity was detected in the solution used. And then the sperm suspension was kept standing at room temperature for 144 hours. The LDH activity was again recognized in the fluid of the suspension and consisted of only LDHx.
LDHx was detected in the cytoplasma of testicular tissues (9 of 10 testes) and epididymal head (1 of 10 epididymides examined). No LDHx was found in any other tissues of accessory sexual organs examined.
In conclusion, LDH activity and LDHx fraction in human ejaculate would be a good index for clinical evalution of the ejaculate.