In recent years, a substantial interest has been aroused in investigating Na(+),K(+) ATPase as a membrane structure which not only performs its direct function in maintaining the gradients of Na(+) and K(+) concentrations, but also may participate in the intracellular signal transduction processes in response to various physiological stimuli. The effect of marinobufagenin, a digitalislike factor, on the growth and proliferation of sensory ganglia, cardiac, retina, skin, and liver tissue explants of 10-12day old chicken embryos was investigated by the organotypic culture method in a wide range of concentrations (10(-10) to 10(-4) M). It was first demonstrated that marinobufagenin inhibited the growth of the investigated tissue explants in the dosedependent but not tissuespecific manner. The experimental data obtained allow us to suggest that the mechanism of regulation of tissue growth by marinobufagenin during the embryonic period of ontogenesis is associated with the modulation of the pump function of Na(+),K(+) ATPase but not its transducing function.