Objectives: 

Intracellular pH (pHi) regulation is an important homeostatic function of cells. There are three major pHi-regulatory mechanisms: The HCO3-/Cl- exchanger (AE), which alleviates alkalosis, and the Na+/H+ exchanger (NHE) and Na+,HCO3-/Cl- exchanger (NDBCE), both of which oppose acidosis. Although AE activity high at GV-stage oocyte it has been inhibited during meiotic maturation. When oocyte reaches at pronuclear stage (PN) zygote, it recovers from this inhibition. After this stage, embryos develop in oviduct which becomes less alkali as the channel get near uterus, even in acidic uterus. Therefore, we worked on AE activity at induced-alkalosis during preimplantation-stages embryos of Balb/c strain mouse.

Materials: 

PPN zygotes, two-cell (2-c), four-cell (4-c), morula and blastocyst stage embryos were obtained by classical procedure from super ovulated female. pHi was recorded using an imaging system attached to epifluorescence microscope. AE activity was determined by using alkalization curve obtained from Cl- removal method. This activity was confirmed by recovery from induced-alkalosis and inhibited by 4,4'–diisocyanatostilbene-2,2' disulphonic acid, disodium salt (DIDS). Differences between groups were determined by using one-way ANOVA, and statistical significance was accepted at p<0.05.

Results: 

We found out that AE activity was statistically higher at PN zygote (0,086±0,008 pHU/min) and 2-c embryo (0,063±0,009) than those of the other stage embryos (4-c, 0,035±0,005; morula, 0,024±0,005; blastocyst, 0,014±0,004). AE activity became lower as embryos developing to blastocyst stage. However, complete recovery from induced-alkalosis was determined at all-stages of embryos. Beside of this, DIDS inhibited these recovery responses.

Conclusions: 

Decrease at AE activity as embryos developing to blastocyst stages has been shown that embryos constitute appropriate regulation in accordance with the environment; from alkaline to acidic surroundings.

This study was supported by TUBITAK (111S156).