Aminoglycoside-induced increase of intracellular calcium in LLC-PK₁ cells due to an artifact caused by trypsin and EDTA

Dietary calcium supplements attenuate experimental aminoglycoside nephrotoxicity. In cultured renal tubular cells, intracellular calcium levels have been reported to rise with aminoglycoside addition to the culture medium. In experiments designed to verify the in vitro influence of calcium on cultured kidney cells, we detected an unexpected artifact. When we resuspended cultured LLC-PK₁ cells with trypsin and EDTA to measure intracellular calcium levels, our results correlated well with previously reported values. However, we saw no increase in intracellular calcium levels when we measured them by digital imaging video microscopy unless trypsin- EDTA exposure preceded aminoglycoside exposure. This apparent artifact should be considered in any study of the effects of various agents on intracellular calcium levels.