PROTECTIVE ENVIRONMENTS FOR ANIMAL SPERM: EVOLUTION OF METHODS AND TOPICAL ASPECTS (REVIEW ARTICLE)

Abstract

A retrospective review of domestic and foreign sources of literature is presented, as well as data of published own research on cryopreservation of animal sperm. The main historical stages of the creation of protective environments for deep freezing of sperm are given. In the 30s of the last century, a phenomenon characterized by the death of spermatozoa upon sharp cooling in the range of positive temperatures was discovered. It is called temperature shock of sperm. To prevent it, it is proposed to add substances containing phospholipids to the composition of diluents. Such environments can contain both simple components - native chicken egg yolk or milk, and high-tech - lipoproteins, isolated phospholipids of various origins. To stabilize protein-lipid complexes of plasma membranes and acrosomes of sperm during the cooling process, carbohydrates are added to the diluents. Sugars are components of energy supply for sperm and, along with salts, they are the main osmotic regulators. A combination of two or three carbohydrates in the medium was traditionally considered necessary. However, the Kharkiv school of reproductive specialists has proven the possibility of creating effective protective environments using only one sugar - sucrose or lactose - based on considerable practical experience. The effectiveness of germ cell freezing is shown depending on the cryoprotectants used. Glycerin is the first known endocellular cryoprotectant, which is still unsurpassed in sperm cryopreservation. Our own experimental data on the effect of combinations of glycerol with substances from the amide group on the main biological indicators of sperm after deconservation are presented. Cryoprotectants dimethylacetamide (DMAC) and dimethylformamide (DMF) were tested in own experiments on stallion semen. The experiments studied the effect of different concentrations of the above-mentioned penetrating cryoprotectants both on the main physiological characteristics of stallion sperm (motility, survival), and on the degree of damage to the membrane apparatus of sperm. The effectiveness of certain combinations of these substances has been proven. Methods of preventing the negative impact of oxygen and the development of lipid peroxidation processes in sperm during cryopreservation are presented. The concept of using additional hormonal components in diluents, in particular prostaglandin F2a, is revealed. The materials related to the effect on the quality of reproductive cells of healing preparations are displayed. Keywords: artificial insemination, environments, semen, animals, bulls, stallions, cryoprotectants, freezing.