Fig. 1. Effects of bicarbonate, albumin, and extracellular calcium on relative cholesterol levels in boar sperm cells incubated for 2 hours in HBT. (a) The relative amount of cholesterol (mol%) is expressed in sperm samples that have been subjected to incubation in HBT (depleted of CaCl₂) containing the indicated additions (i.e. combinations of 1 mM EGTA, 2 mM CaCl₂, 15 mM NaHCO₃, 0.3% (w/v) BSA; sperm samples were washed through Percoll prior to lipid extraction). Mean values of three independent experiments (measured in triplicate) are indicated (error bars represent s.d. values; , P<0.001). (b) Absolute amounts (µg/10⁹ cells) of the major lipid classes in the corresponding samples that were incubated in HBT (open bars) and HBT-Bic supplemented with 0.3% (w/v) albumin (filled bars). Major lipid classes: cholesterol (chol), phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylserine (PS), sulfogalactosyl glycerol (SGG), sphingomyelin (SM). Mean values of three independent experiments (measured in triplicate) are indicated (error bars represent s.d. values, , P<0.001). (c) Relative composition (mol%) of the most abundant lipid classes that were extracted from plasma membrane fractions derived from sperm suspensions incubated in HBT (open bars), HBT-Bic (hatched bars) and HBT-Bic supplemented with 0.3% (w/v) albumin (filled bars). Mean values of one experiment measured in triplicate.