AbstractIntranuclear Na, K and Mg concentrations were determined in cells of salivary glands incubated for 1hin selected NaCl/KCl/MgCl2media. By variation of the external milieu beyond “physiological” limits the intranuclear electrolytes can be shifted between ca 100 and 280 mM [K]i, between ca 8 and 100 mM [Na]iand between ca 5 and 75 mM [Mg]i. No significant competition or interactions of the 3 ionic species are apparent. The relationships [K]e: [K]iand [Na]e: [Na]ican best be described by a positive and linear, that between [Mg]e: [Mg]iby a negative and exponential function. Regression parameters are given which permit a computation of intranuclear [Na], [K]and [Mg] as induced by NaCl/KCl/MgCl2in any binary or triple combination that is tolerated by the explanted gland without visible dam