Alteration of tyrosine aminotransferase activity in hepatoma cells in tissue culture by amphotericin B.

Two clonal lines of rat hepatoma cells, in tissue culture, that have steroid-inducible tyrosine aminotransferase (TAT) activities were shown to have different responses to amphotericin B. One of the cell lines (HTC) was relatively resistant to the growth-inhibiting effects of amphotericin B and demonstrated an inhibition of only its steroid-inducible TAT activity when exposed to the antifungal agent. In contrast, not only was the other cell line (MHC) sensitive to amphotericin B during its growth, but uninduced and induced enzyme activities were affected. During the first few hours after the exposure of MHC cells to amphotericin B, both basal and dexamethasone-induced TAT activity were reduced; with continued exposure, enzyme activity increased over that of untreated cells and was superinduced in the presence of maximal, stimulating amounts of steroid. The mechanisms by which enzyme activity is induced by amphotericin B are probably different from those mediated by steroids.