Arrest at metaphase of meiosis I in starfish oocytes in the ovary is maintained by high CO2 and low O2 concentrations in extracellular fluid.
Zoolog Sci
; 30(11): 975-84, 2013 Nov.
Article
en En
| MEDLINE
| ID: mdl-24199863
ABSTRACT
During the spawning process in starfish, oocytes are arrested at metaphase of meiosis I (MI) within the ovary, and reinitiate meiosis only after they have been released into the seawater. However, this arrest does not occur if the ovary is removed from the animal. As the pH of the coelomic fluid is buffered by CO2/H(+)/HCO3(-), we investigated the involvement of gas concentrations in MI arrest. In vivo, the CO2 level in the coelomic fluid was high (â¼1.5% vs. 0.04% in air) and the O2 level was low (0.1-1.0% vs. â¼20% in air). When these gas conditions were reproduced in isolated coelomic fluid or seawater, ovarian oocytes arrested at MI, just as in vivo. Isolated oocytes from the ovary required the similar high CO2 and low O2 level to remain arrested in MI and had an intracellular pH of â¼6.9. Intracellular pH increased to â¼7.3 when oocytes were transferred to seawater equilibrated with air, a condition that mimics that of spawning. We used ammonium acetate to clamp intracellular pH at different levels and found that MI arrest occurred when intracellular pH was â¼6.9. Our results support the idea that high CO2 and low O2 in the ovarian environment lead to low intracellular pH and MI arrest, while spawning into the seawater with low CO2 and high O2 results in high intracellular pH and release from MI arrest. The biological significance of MI arrest is that oocytes are spawned into seawater at the optimal physiological state of MI when the least polyspermy occurs.
Texto completo:
1
Banco de datos:
MEDLINE
Asunto principal:
Oocitos
/
Oxígeno
/
Estrellas de Mar
/
Dióxido de Carbono
/
Líquido Extracelular
/
Meiosis
Límite:
Animals
Idioma:
En
Revista:
Zoolog Sci
Asunto de la revista:
BIOLOGIA
Año:
2013
Tipo del documento:
Article
País de afiliación:
Japón