Uptake and distribution of chromium in isolated rat hepatocytes and its relation to cellular injury

In order to study the difference of uptake and distribution between hexavalent (Cr6+) and trivalent (Cr3+) chromium in isolated rat hepatocytes, the cells were incubated with Cr6+ or Cr3+ (1 mM Cr) at 37 degrees C for up to 60 min. Leakage of lactate dehydrogenase from the hepatocytes into the suspension medium as an indicator of cellular injury was facilitated by Cr6+ (K2Cr2O7) at 60 min of incubation, whereas Cr3+ [Cr(NO3)3] had no effect. After 60 min of incubation with Cr6+, about 33% of the added Cr was found in the hepatocytes, whereas incubation with Cr3+ resulted in transfer of about 66% of the added Cr to the cells. After 20 and 40 min of incubation with Cr6+, about 39% of cellular Cr was found in the cytosolic fraction of hepatocytes, followed by a reduction to about 35% after 60 min of incubation. However, Cr detected in the cytosolic fraction of hepatocytes incubated with Cr3+ was about 1% of cellular Cr. Cr-binding substances in the cytosolic fraction of hepatocytes incubated with Cr6+ were eluted with two Cr peaks by Sephadex G-200 chromatography. These Cr-binding substances in the low-molecular-weight fractions were separable into at least two substances by thin-layer chromatography. These results suggest that Cr6+ readily passes through the cell membrane and combines with substances already present in the cytosolic fraction of hepatocytes, unlike metallothionein induced by cadmium, followed by detoxification. Consequently, cellular injury might be induced by Cr6+ which could not combine with LMCr in the cytosolic space of the hepatocytes.