The urine mutagenicity assay system. Studies related to recovery, storage and concentration procedures

Studies were conducted to determine (i) the effect of storage on the mutagenic activity of urine spiked with known mutagens, (ii) the efficiency of XAD-2 column on the recovery of complex mixtures from spiked urine samples, and (iii) whether the addition of XAD-7 resin to the column and/or the addition of methylene chloride to the elution process increases the recovery of mutagens from urine samples spiked with complex mixtures. Chemically spiked or nonspiked urine samples were concentrated with XAD resin and were tested for mutagenic activity with the Ames Salmonella/microsome assay system. The results indicate that the mutagenic activity of chemically spiked urine remains essentially unchanged after 7 d, but it decreases by approximately 50% for some compounds after 28 d of storage at -70 degrees C. The recovery of mutagens from mutagen-spiked urine varied from 0% to more than 100%. Mutagenic activities of concentrates from urine samples spiked with complex mixtures were higher if resin columns were eluted with both methylene chloride and acetone than with acetone alone. A slight increase in mutagenic activity was also found if a mixture of XAD-2 and XAD-7 instead of XAD-2 alone was used to concentrate urine spiked with air particle extracts.