Kinetic characterization of the changes in protein tyrosine phosphorylation of membranes, cytosolic Ca2+ concentration and viability in boar sperm populations selected by binding to oviductal epithelial cells

On reaching the oviduct, spermatozoa are retained in the isthmic region of the oviduct until ovulation occurs. The essential steps of capacitation are co-ordinated in this region. In this study, a primary cell culture system of oviductal epithelial cells was established to investigate sperm binding to oviductal epithelium and modulation of sperm function during incubation under capacitating conditions in coculture with oviductal epithelial cells. Epithelial cells were stripped from the oviducts of sows and cultivated fo r 5-7 days on Lab-Tek Chamber slides on Matrigel. The preparations on chamb er slides and suspensions of control spermatozoa were incubated for 3 h in Tyrode's albumin lactate pyruvate (TALP) medium. At 3, 30, 60, 90 and 180 m in the free-swimming spermatozoa were collected by washing, and membrane in tegrity, tyrosine phosphorylation patterns and [Ca2+]i of bound, unbound an d control spermatozoa were assessed with fluorescent probes (propidium iodi de, Cy-3 and fluo-3-AM). The cells bound to oviductal epithelia[ cells show ed reduced cytosolic Ca2+ concentration, reduced and almost absent tyrosine phosphorylation of membrane proteins and higher viability at the time of t he first sampling. Increases in Ca2+ concentration and cell death occurred much more slowly during incubation in cells bound to oviductal epithelial c ells compared with free-swimming spermatozoa, and no changes in tyrosine ph osphorylation were observed. The preferential binding of viable, low-Ca2+ c ells with suppressed tyrosine phosphorylation and slower functional modulat ion of boar spermatozoa attached to oviductal epithelia] cells might repres ent a mechanism for selecting functionally competent spermatozoa and prolon ging their lifespan by delaying capacitation in the oviductal reservoir.