The study of osmotic parameters of cells is an important step in successful cryopreservation. The aim of this work was to study the osmotic reactions of cells of different taxonomic groups (euglenoid Astasia longa, microalga Dunaliella salina) in response to complementing with of promising cryoprotectants (Me₂SO₄, glycerol, ethanol) under normothermic conditions.

Addition of 1-10% Me₂SO₄ solutions to A. longa cells led to a change in cell shape, loss of plait and motility, reduction of the relative area of cells by 10-27%, which after washing is restored only partially. The 1% ethanol and 1-5% glycerol solutions did not affect the condition of A. longa cells. The 5-10% ethanol solutions decreased the cell area by 78.93-82.88%, the cells lost harnesses and mobility. A. longa was insensitive to 1-5% glycerol solutions; at 10% solution single cells lose flagella, cell area decreased by 70.8%. Rehydration occurred instantly.

Complementing with of 1-30% glycerol to the suspension of D. salina cells did not affect their condition. Exposure to 1-30% Me₂SO₄ did not significantly affect the relative area and did not lead to irreversible plasmolysis. Addition of 1-10% ethanol solutions did not lead to cell death, and the relative area decreased by 3-30%. Washing of all samples helped to restore the relative area and shape.

Thus, D. salina cells are osmotically tolerant to different concentrations of promising solutions of cryoprotectants. Whereas A. longa is more vulnerable to osmotic stress and can withstand only short-term exposure with 1-5% solutions of ethanol and glycerol.