LDH-X, an
isoenzyme of
lactate dehydrogenase specific for germinal epithelium activity, has been measured in the seminal plasma of infertile subjects whose
infertility had different origins. In the same samples, seminal
transferrin, an index of Sertoli cell function, was also measured. In this investigation, seminal
LDH-X was not detectable in the vasectomized subjects, in patients with
azoospermia due to seminiferous tubular damage, nor in patients who showed a marked decrease in sperm concentration (less than 1 X 10(6)/ml). In oligozoospermic patients (sperm concentration less than 20 X 10(6)/ml) seminal
LDH-X levels were reduced to about one-third of those found in normal controls. Seminal
LDH-X levels correlated (r = 0.7237) with total sperm count better than seminal
transferrin levels (r = 0.5511), while no correlation was found between these two biochemical parameters and sperm motility, viability and morphology. To study their spontaneous variations with time,
LDH-X and
transferrin were also measured in semen specimens collected monthly from five healthy men, over 1 year. In these samples (N = 60), sperm count variability (43.1%, calculated in terms of the coefficient of variation), was similar to that of
LDH-X (40.4%) and higher than for
transferrin (23.0%).