3-day effect of low temperature increases the amount of extraerythrocyte hemoglobin by 64% in the blood serum, the activity of glucose-6-phosphatedehydrogenase increasing by 231%. Administration of 6.12 or 18 micrograms/100 g body weight of the delta-sleep peptide (DSIP) induces on change in amount of extraerythrocyte hemoglobin in the blood serum of intact rats. 6 micrograms/100 g DSIP increases the activity of glucose-6-phosphatedehydrogenase by 251.6%; 12 micrograms/100 g-- by 165.6%; 18 micrograms/100 g--by 90.6%. The normalizing effect on the level of extraerythrocyte hemoglobin and activity of glucose-6-phosphatedehydrogenase in low ambient temperature occurs at the dose of DSIP 12 micrograms/100 g body weight. The DSIP stabilizes the erythrocyte membranes in low temperature.