The distribution of sodium, potassium and chloride in the nucleus and cytoplasm of Bufo bufo oocytes measured by electron microprobe analysis.

Abstract

Measurements of cytoplasmic and nuclear Na, K and Cl were made by electron microprobe analysis on freeze-dried sections of oocytes of B. bufo using standards of bovine plasma albumin and .gamma.-globulin. Concentrations were obtained per kg dry mass, converted to concentrations per l of water content using known figures for water and solid concentration of nucleus and cytoplasm and compared with measurements on cells from the same animal obtained by flame photometry. In fresh oocytes concentrations were (mean .+-. SE of mean in mmol/l H2O) in cytoplasm Na 10.9 .+-. 1.95, K 70.2 .+-. 3.22, Cl 98.8 .+-. 11.0, and in nucleus Na 10.4 .+-. 1.79, K 266.4 .+-. 22.8, Cl 91.3 .+-. 9.0. After treatment with Na-free Ringer (Li substituted for Na) for 5 h, concentrations were in cytoplasm Na 11.1 .+-. 2.44, K 64.4 .+-. 5.7 and Cl 88.7 .+-. 8.8 and in nucleus Na 2.4 .+-. 0.73, K 141 .+-. 13.9 and Cl 75.0 .+-. 6.7. Na inexchangeable with Li therefore, lays in the cytoplasm but not in the nucleus as previously shown by autoradiography. For K EM analysis measurements agreed well with those obtained by flame photometry but the former measured only 35% of Na measured by flame photometry. This discrepancy may be due either to technical difficulties with the electron microprobe analysis or to localization of Na in the cytoplasm.