| Popis: |
Accumulation of Na+ and K+ ions in oocytes of the river lamprey Lampetra fluviatilis and their transport across the plasma membrane is realized by two main mechanisms--Na,K-pump and Na,K,Cl-cotransport. At the prespawning period from December to May the intracellular Na+ concentration was observed to increase from 10 to 25 mM and the K+ concentration--from 28 to 45 mM. Results obtained on isolated oocytes with aid of 204Tl radioactive label have shown that contributions of the Na,K-pump and Na,K,Cl-cotransport to potassium accumulations were close until March. In spring, the total K+ inflow almost doubled owing to activation of the Na,K-pump, whereas contribution of Na,K,Cl-cotransport did not change. It seems that an increase of the intracellular content of the main inorganic cations in oocytes resulted in parallel activation of the Na,K-pump and probably of Na/H-exchange. The biological significance of activation of these mechanisms of ion transport at the prespawning period might be due to a necessity of accumulation of Na+ and K+ ions in concentrations optimal for subsequent embryonic development. |
