title: Membrane contact with oviductal epithelium modulates the intracellular calcium concentration of equine spermatozoa in vitro.
abstract: Interaction of equine spermatozoa with oviductal epithelial cells (OEC) prolongs sperm viability and maintains low intracellular calcium concentration ([Ca2+]i) in spermatozoa. Experiments were designed to investigate 1) whether release of spermatozoa from OEC in vitro is associated with elevated [Ca2+]i and 2) whether soluble products from OEC or direct membrane contact between spermatozoa and OEC mediates the effects of OEC on sperm [Ca2+]i. In the first experiment, changes in [Ca2+]i in spermatozoa loaded with indo-1 acetoxymethylester were determined in motile spermatozoa released from OEC monolayers after 4 h of culture compared to [Ca2+]i in spermatozoa still attached to OEC. In addition, [Ca2+]i was determined in spermatozoa incubated with OEC-conditioned medium for 6 h compared to that in spermatozoa incubated in control medium. [Ca2+]i was higher in motile spermatozoa released from OEC than in spermatozoa still attached to OEC after 4 h of incubation. Incubation in OEC-conditioned medium resulted in lower sperm [Ca2+]i only at 4 h of incubation, but not at 0.5, 2, or 6 h of incubation. In the second experiment, a suspension of apical plasma membrane vesicles (AMV) isolated from isthmic oviductal epithelium was used to study the specific effect of sperm contact with OEC membranes on sperm viability, capacitation, and [Ca2+]i. Direct membrane contact between spermatozoa and AMV prolonged sperm viability, delayed capacitation, and maintained low [Ca2+]i in spermatozoa. These results indicated that membrane contact between equine spermatozoa and OEC is required to maintain low [Ca2+]i, delay capacitation, and prolong viability of spermatozoa in vitro. Modulation of capacitation rate for spermatozoa stored in the isthmic sperm reservoir might ensure the availability of a competent sperm population at the time of fertilization.
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA.
authors.forename: I
authors.initials: I
authors.lastname: Dobrinski
authors.forename: T T
authors.initials: TT
authors.lastname: Smith
authors.forename: S S
authors.initials: SS
authors.lastname: Suarez
authors.forename: B A
authors.initials: BA
authors.lastname: Ball
mesh_terms: D000177:Acrosome / Q000648:ultrastructure; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002450:Cell Communication; D002462:Cell Membrane / Q000502:physiology; D002470:Cell Survival; D002478:Cells, Cultured; D002614:Chelating Agents; D017077:Culture Media, Conditioned; D004848:Epithelium / Q000502:physiology; D005187:Fallopian Tubes / Q000502:physiology*; D005260:Female; D006736:Horses; D007700:Kinetics; D008297:Male; D013075:Sperm Capacitation; D013077:Sperm Head / Q000648:ultrastructure; D013081:Sperm Motility; D013094:Spermatozoa / Q000166:cytology / Q000502:physiology*
chemical_list: D002614:Chelating Agents; D017077:Culture Media, Conditioned; D002118:Calcium