A pressing need exists to develop and validate molecular
biomarkers to assess the early effects of chemical agents, both individually and in mixtures. This is particularly true for new and chemically intensive industries such as the
semiconductor industry. Previous studies from this laboratory and others have demonstrated
element-specific alterations of the
heme biosynthetic pathway for the III-V
semiconductors gallium arsenide (
GaAs) and
indium arsenide (
InAs) with attendant increased urinary excretion of specific
heme precursors. These data represent an example of a metabolomic
biomarker to assess chemical effects early, before clinical disease develops. Previous studies have demonstrated that the intratracheal or subcutaneous administration of
GaAs and
InAs particles to hamsters produces the induction of the major
stress protein gene families in renal proximal tubule cells. This was monitored by 35-S
methionine labeling of gene products followed by two-dimensional gel electrophoresis after exposure to
InAs particles. The present studies examined whether these effects were associated with the development of compound-specific
proteinuria after 10 or 30 days following
subcutaneous injection of
GaAs or
InAs particles in hamsters. The results of these studies demonstrated the development of
GaAs- and
InAs-specific alterations in renal tubule cell
protein expression patterns that varied
at 10 and 30 days. At the 30-day point, cells in hamsters that received
InAs particles showed marked attenuation of
protein expression, suggesting inhibition of the
stress protein response. These changes were associated with
GaAs and
InAs proteinuria patterns as monitored by two-dimensional gel electrophoresis and
silver staining. The intensity of the
protein excretion patterns increased between the 10- and 30-day points and was most pronounced for animals in the 30-day
InAs treatment group. No overt morphologic signs of cell death were seen in renal tubule cells of these animals. Western blot analyses of the urines with
antibodies to the 32-, 70-, and 90-kDa
stress protein families did not show the presence of these molecules, indicating that these
proteins were not excreted in the urine samples. These data suggest that the observed
proteinuria patterns were not a result of cell death and that the observed chemical-specific
proteinurias were produced before marked cellular toxicity. These findings suggest a hypothesis involving
GaAs and
InAs interference with
stress protein chaperoning of reabsorbed
proteins for proteosomic degradation and the probable chaperoning of damaged intracellular
proteins from renal proximal tubule cells into the urinary filtrate. Overall, the results of these studies provide further information on the nephrotoxicity of these
semiconductor compounds. They also suggest the use of two-dimensional gel electrophoresis with
silver staining of urinary
protein patterns as a potentially useful proteomic approach to renal damage early in relation to intracellular proteotoxicity in kidney tubule cells.