Seminal LDH-C4 isoenzyme and sperm mitochondrial activity: a study in male partners of infertile couples

Lactate dehydrogenase isoenzyme patterns were obtained in the seman of 93 male partners of infertile couples and 28 proven fertile subjects as a control group. Sperm mitochondrial activity index (SMAI) alongwith the conventional seminal parameters was studied for all the subjects excepting the azoospermic and vasectomised males. Only LDH-C4, a germ cell specific isoenzyme activity varied with the variation in sperm density. LDH-C4 activity varied significantly (p<0.001) within and between different groups. Lactate dehydrogenase-C4 activity was absent in 17 azoospermic samples, confirming its germinal epithelial origin, as well as in 8 samples of vasectomised males. In one azoospermic sample, there were many immature germ cells along with surprisingly high LDH-C4 activity suggesting more activity of germinal epithelium associated with high LDH-C4 activity. LDH-C4 activity was reduced significantly in oligozoospermic samples in proportion to sperm density, thus confirming strong correlation (p<0.001) between LDH-C4 and sperm density. There was statistically significant correlation between LDH-C4 and percentage sperm motility as well as between LDH-C4 and Sperm Mitochondrial Activity Index (SMAI) (probability varying from p<0.05 to p<0.01 in different groups), but no such correlation was found between LDH-C4 and sperm morphology. The data confirms LDH-C4 as a germinal epithelial marker. Its relationship with percentage sperm motility is suggestive of definite role of LDH-C4 in evaluation of the spermatozoal quality, similarly its relationship with Sperm Mitochondrial Activity Index (SMAI score) suggest the role of LDH-C4 in metabolism of the spermatocytes and sperms, though further studies are required for clear and detailed understanding of its metabolic role in semen.