Ag+ alters cell growth, neurite extension, cardiomyocyte beating, and fertilized egg constriction

Background: The Russian Space Agency uses electrochemically generated silve r ions (Ag+) to purify drinking water for their space station, Mir, and the ir portion of the International Space Station. U.S. EPA guidelines allow 10 .6 mu mol.L-1 Ag+ in human drinking water for up to 10 d. Studies correlate Ag+ exposure with tissue dysfunction in humans, rats, and mice, and with a ltered ion transport, skeletal muscle contraction, and embryonic cell const riction in other animal cells. Ag+ effects on cell shape change-related fun ctions have not been assessed. Methods: immortalized embryonic human intest inal epithelial cells, freshly explanted embryonic avian nerve cells and ca rdiomyocytes, and marine fertilized eggs were grown in vitro in medium cont aining AgNO3. Results: Intestinal cells detach from the substratum and viab le cell number decreases by 5-6 d at 5 mu mol.L-1 AgNO3, and faster at high er concentrations. Microtubules appear unaltered in adherent cells. Detache d cells are nonviable. Neurite outgrowth and glial cell migration from dors al root ganglia are inhibited by 3 d at 15 mu mol.L-1 AgNO3 or greater. Con tractions stop temporarily in most cardiomyocytes by 5 min at 5 mu mol.L-1 AgNO3 or more, but some cardiomyocytes beat 3 times faster than normal at 7 .5-20 mu mol.L-1 AgNO3. Picomolar Ag+ increases marine egg polar lobe const riction within an hour, even in the absence of microtubules. Conclusion: Ag + alters animal cell growth and shape changes by a MT-independent mechanism . This is the first report of Ag+ effects on vertebrate neurite outgrowth, glial cell migration, or cardiomyocyte beat rate.