CHARACTERISTICS OF CALCIUM-ION INFLUX INDUCED BY HUMAN FOLLICULAR-FLUID IN INDIVIDUAL HUMAN SPERM

The mechanism of Ca2+ influx into human spermatozoa was investigated. Human follicular fluid (hFF), which contains progesterone, stimulated an increase in the concentration of intracellular free Ca2+ ([Ca2+](i) ) as measured by fluorescence spectroscopy using Fura-2/AM. The techni que allowed the measurement of [Ca2+](i) in individual, motile spermat ozoa, by improvement of the previous methods. The role of Ca2+ channel s was investigated using selective blocking agents. Neither blockade o f L-type channels with verapamil or lanthanum (La3+) nor blockade of N -type channels with omega-conotoxin affected the hFF-stimulated increa se in [Ca2+](i). Blockade of T-type channels with either nickel (Ni2+) or amiloride significantly reduced the hFF-stimulated increase in [Ca 2+](i) and amiloride significantly decreased baseline [Ca2+](i). Incub ation of sperm in Na+-free medium did not affect [Ca2+](i), indicating that Na+/Ca2+ exchange has no major role in Ca2+ influx. The results suggest that calcium influx induced by hFF occurs via T-type voltage-i ndependent Ca2+ channels. The method described allows accurate measure ment of [Ca2+](i) in individual, motile human spermatozoa.