A study of the osmotic sensitivity of pike (Esox lucius, L., 1758) spermatozoa for the optimization of their cryopreservation

Purpose. The study of the osmotic sensitivity of pike (Esox lucius, L., 1758) spermatozoa. Methodology. The osmotic response of pike spermatozoa was investigated by spectrophotometry method based on the kinetics of light transmission of cells suspensions, which were placed in distilled water and 10?200 mOsm/kg solutions of NaCl . Measurements of light transmittance were carried out using photoelectrocolorimeter KF-77 (ZALIMP, Poland), equipped with a magnetic stirrer and thermostatted sample compartment. The coefficient of permeability of spermatozoa plasma membrane for water molecules (Lp) was determine by approximation of the experimental time dependences of the relative volume by solutions of the equations of modified Kedem-Kachalskyi physical-mathematical model of transmembrane mass transport. The activation energy (Еа) of the substances transfer across the cell membrane was calculated taking into account lnLp(1/T) dependencies. Findings. The characteristic time of water penetration is about 40-50s within 100-200 mOsm/kg range (12 °C). Membrane permeability coefficient of pike spermatozoa for water molecules is 5.43 - 1.15 - 10-15 m3/Ns. The decline in coefficient of membrane permeability for water molecules in the range of 25?10 °C is characterized by the activation energy of water transfer, which is 64±5 kJ/mol, that indicates about water molecules penetration into spermatozoa via a passive diffusion through the lipid bilayer. Hypoosmotic resistance of pike spermatozoa, estimated as time before lysis of 50% cells incubated in distilled water, is 70?110 s (12 °C). Developed approaches also can be used as simple and quick tests of the functional state of cell membranes. Originality. The coefficient of plasma membranes permeability of pike spermatozoa and its temperature dependence were defined for the first time. Practical value. The results are used in the design of media and modes of pike sperm cryopreservation.