Elemental content in the nucleus and in yolk and yolk‐free cytoplasm of developing Rana pipiens oocytes: An X‐ray microanalysis study

Energy dispersive x‐ray microanalysis measured the Na, K, Cl, P, Mg, S, and Ca contents (mM/kg dry weight) in the nucleus, yolk‐free cytoplasm, and yolk platelets of Rana pipiens oocytes quick frozen in the ovary. The data revealed that significant content changes occur in frog oocytes during intraovarian growth. All elements but Ca changed in content in the nucleus and cytoplasm, while in the yolk platelet only Na content did not change. A nucleus to cytoplasm K gradient develops and increases in magnitude during oocyte growth. The data from this and previous reports lead to the hypothesis that intra‐oocytic water and elements undergo changes in state during oocyte growth and that three subcellular Na compartments exist.