The concentrations of water, sodium and potassium in the nucleus and cytoplasm of amphibian oocytes

Abstract

Techniques are described for the isolation of nuclei and cytoplasm from frozen amphibian oocytes at -40 °C and their analysis for water, sodium, and potassium contents. Nuclei of the 4 species studied contain 74-85% water while cytoplasm is only 35-50% water. Nuclei contain 7-17 µequiv. Na/ml H₂O and 123-129 µequiv. K/ml H₂O; cytoplasm contains 59-84 µequiv. Na/ml H₂O and 81-94 µequiv. K/ml H₂O. Mechanisms suggested to explain the observed nucleo-cytoplasmic asymmetries are the selective sequestering of sodium in the cytoplasm and a fraction of cytoplasmic water which does not act as solvent. Asymmetric cation transport by the nuclear membrane is not indicated.