CHEMOTAXIS AND CHEMOKINESIS OF HUMAN SPERMATOZOA TO FOLLICULAR FACTORS

Human spermatozoa accumulate in vitro in diluted follicular fluids obt ained from follicles from which the eggs have been fertilized. Using c apillary assays under a variety of experimental conditions (ascending or descending gradients of follicular fluid, or no gradient at all) an d microscopic assays in which individual spermatozoa could be followed , we found that the sperm accumulation in follicular fluid was the res ult of both sperm chemotaxis and chemokinesis and eventually hyperacti vation-like motility, We determined the optimal conditions for sperm a ccumulation, which involved sperm preincubation (possibly to induce sp erm capacitation) and proper dilution of follicular fluid. In all the assays, the not accumulation was low, probably reflecting the chemotac tic responsiveness of only a small fraction of the sperm population at any given time. We partially fractionated follicular fluid in a Centr icon microconcentrator (Amicon, Danvers, MA) and by acetone precipitat ion, and found that at least one of the chemotactic factors is a small (< 10-kDa) molecule that is probably nonhydrophobic. This is the firs t time that sperm chemotaxis and chemokinesis in response to a follicu lar factor(s) in mammals has been established and has been distinguish ed from other processes that might cause sperm accumulation. The physi ological significance of these findings is discussed.