Cholesterol supplementation of bovine sperm

Bull sperm were treated with a range of cholesterol-loaded cyclodextrin (CLC) concentrations and frozen in an egg yolk Tris or sodium citrate diluent. After thawing, the percentages of motile sperm in the 1.5mg CLC treatment (Tris) were higher (60%) than control (0mg CLC) sperm (42%; P < 0.05) but no differences were detected with the sodium citrate diluent (P > 0.05). Bull sperm treated with 3.0mg CLC and frozen in Tris diluent had more viable cells (66%) compared to the control (48%; P < 0.05).; Analysis of cholesterol incorporation by spectrofluorometry and HPLC demonstrated that cholesterol content of bull sperm increases with CLC treatment (R2 = 0.824) and flow cytometry illustrated uniform cholesterol incorporation (CV = 12.9% +/- 0.73).; Bull sperm were analyzed for calcium levels and ability to acrosome react when treated with dilauroylphosphatidylcholine (PC-12), calcium ionophore A23187 (A23187) or heparin. Fresh sperm treated with 1.5mg CLC accumulated calcium slower compared to control sperm when capacitated with PC-12 or A23187 (P < 0.01). After cryopreservation, CLC treated sperm accumulated calcium slower when capacitated with PC-12 only. CLC treatment decreased the acrosome reaction rate compared to control for fresh sperm, when capacitated with A23187 or heparin (P < 0.05) but no differences were detected following cryopreservation.; In vitro fertilization using frozen thawed bull sperm treated with 0 or 1.5mg CLC prior to cryopreservation resulted in no differences in fertility (P > 0.05).; A breeding trial using dairy heifers resulted in similar pregnancy rates for control (50%) and for sperm treated with 1.5mg CLC (59%; P > 0.05).; Addition of CLC (1.5mg) to CHO cells analyzed for membrane fluidity at 23°C or at 5°C resulted in decreased fluidity compared to control cells. When CHO cells were cryopreserved (control and CLC treatments) membrane fluidity decreased. Bull sperm form 2 distinct populations of cells compared to the single population in CHO cell fluidity analyses. At 23°C, bull sperm treated with CLC showed reduced membrane fluidity and cells converting from the high to the low fluidity population, as CLC concentration increased (P < 0.05). After cooling to 5°C, CLC treated cells converted to the more fluid population (P < 0.05). Following cryopreservation, both populations of sperm were less fluid than unfrozen cells (P < 0.05).