Changes of HCO3- / Cl- exchanger activity during meiotic maturation on mouse oocyte / zygotes

Changes of HCO3- / Cl- Exchanger Activity During Meiotic Maturation on MouseOocyte / ZygotesIntracellular pH regulatory systems of growing mouse oocytes are acquired withmeiotic competence, and when oocyte reaches to germinal vesicle (GV) stage theybecome full activity. But there are some evidence about these systems are inhibited onmeiotic maturation process. It has been determined that activity of Na+/H+ exchangerwhich is defence mechanism against acid shock is inhibited in this process. On the otherhand, we found evidence about gradually increasing activity of Na+,HCO3 -/Cl-exchanger which is other defence mechanism against acidosis in this process. The aimof this study was investigate relationship between meiotic maturation and activity ofHCO3-/Cl- exchanger (AE) which protects cells against to alkalosis.GV, Metaphase I (MI), Metaphase II (MII) oocytes and pronuclear (PN)zygotes were obtained from Balb/c strain mouse following superovulation protocol.KSOM based solutions were used as culture and recording solutions. Intracellular pH(pHi) was recorded by using microspectrofluorometric tecnique from oocytes/zygoteswhich were loaded with pH-sensitive florofore, SNARF-1-AM.While AE acitivity was high at GV stage oocytes (0,056±0,008 pHU/min), thisacitivity was significantly inhibited at MI and MII stages (respectively, 0,024±0,006pHU/min and 0,030±0,004 pHU/min; p<0,05). AE acitivity reached higher level at PNzygote stage (0,040±0,004 pHU/min). Determined all these activities were significantlyinhibited by DIDS at studied all oocyte and zygote stages. While pHi of MI and MIIstage oocytes was not completely recover from induced alkalosis (respectively,7.18±0,008 vs 7,45±0,041; 7,22±0,002 vs 7,43±0,040), almost completely recover wereoccur at GV stage oocytes and PN zygotes (respectively, 7,20±0,017 vs 7,27±0,029;7,16±0,015 vs 7,29±0,035).HCO3-/Cl- exchanger has been inhibited during meiotic maturation processwhich is a important milestones on development of oocyte. This inhibition has beenpersisted till PN stage zygote following fertilization. The physiologic significance ofinhibition of AE activity is not known yet but it may be related to metabolic activationduring fertilization process.Key Words: Anion exchanger, mouse, intracellular pH regulation, meioticmaturation, oocyte