IONIZED CALCIUM IN HUMAN MALE AND FEMALE REPRODUCTIVE FLUIDS - RELATIONSHIPS TO SPERM MOTILITY

The levels of ionized calcium in seminal plasma were - 20% of the serum levels. In contrast, cervical mucus contained a level of ionized calcium similar to both serum and follicular fluid. Titration of seminal plasma and serum with increasing concentrations of calcium chloride indicated a 10-fold higher calcium-binding capacity for seminal plasma. In a random group of men under semen investigation, concentrations of ionized calcium and citrate in semen were inversely correlated (r = 0.732; P > 0.001), an observation which was confirmed by studies of split ejaculates. These findings supported the contention that citrate is the major regulator of the levels of ionized calcium in seminal plasma and primarily responsible for maintaining the calcium gradient between the seminal plasma and cervical mucus. No significant relationship could be demonstrated between the levels of ionized calcium in the ejaculates and any of the motility characteristics of the spermatozoa in the same sample. Furthermore, the addition of increasing quantities of calcium chloride (0.16-20.00 mM) to washed spermatozoa had no major effects on their progressive motility. These data suggest that human spermatozoa are effective in maintaining an appropriate level of internal ionized calcium, necessary for normal motility, despite fluctuations in external calcium. © 1990 Oxford University Press.