Figure 1. Protocols of vitrification and warming of oocytes to T4 and ING groups. Note: Oocyte vitrification procedure. Mouse oocytes were transferred to HTF medium regardless of the experimental group. Vitrification phase: T4 protocol (left) comprised the oocyte exposure to equilibration solution 1 (ES-20 µL drops) and vitrification solution 2 (VS - 20 µL drop); the ING protocol (on the right side) included the vitrification solution 1 (VI-1 - 20 µL drop) and vitrification solution 2 (VI-2- 20 µL drop). After loading using the open pulled straw (OPS) protocol, oocytes were immersed in liquid nitrogen until 90s. Warming phase: oocytes were warmed by T4 protocol (left) using a thawing solution 1 (TS - 250 µL drop), dilution solution (DS - 50 µL drop) and washing solution (WS - 25 µL drop); ING protocol (on the right side) comprised a thawing solution 1 (DV-I - 250 µL drop), thawing solution 2 (DV-II - 100 µL drop) and DV-III (100 µL drop). After warming, the next step was the recovery culture (incubation in IVF culture medium with 20 % (v/v) protein supplement for 2 h at 37 °C). HTF = Human Tubal Fluid medium; T4 = Tvitri-4 medium; ING = Ingámed medium.