A comparison of the ability of frog and rat S‐9 to activate promutagens in the Ames test

Abstract

A mutagenesis assay employing the frog, Rana pipiens, is currently under development [McKinnell et al, 1979]. A question that must be answered is whether the frog is metabolically capable of activating a large number of promutagens. The Ames assay offers a simple means of comparing the metabolism of mutagens by different animal species. The Ames response obtained with frog-liver S-9 was compared to the response with rat-liver S-9, using the following compounds: Benzo(a)pyrene, 7,12-dimethylbenz(a)anthracene, 2-amino-fluorene, azobenzene, Sudan II, dibutylnitrosamine, hydrazine sulfate, hydroxyethylhydrazine, cyclophosphamide, 1,2-dichloroethane, tris(2,3 dibromopropyl)phosphate, diallate, quinoline, quercetin, aflatoxin B 1, emodin, and safrole. Of these compounds, activation by rat S-9 was observed for all except hydrazine sulfate and safrole. All except Sudan II, 1,2-dichloroethane, quinoline, and safrole gave positive Ames responses with frog S-9. In general, the responses with frog S-9 were quantitatively lower than those obtained with Aroclor-induced rat S-9; however, the optimum procedure for frog-liver induction has not been determined. The response to dichloroethane is very sensitive to the amount of activating enzyme present; it might be positive with optimally induced frog S-9. Thus, only two of the 15 compounds positive with rat S-9 were definitely missed when tested with frog S-9. We feel that the frog assay appears to be promising from the standpoint of false-negatives.

Joint FAO/WHO Expert Committee on Food Additives (JECFA)

“…Negative results were reported using the Ames assay for safrole tested at concentrations of up to 5000 μg/plate, with and without metabolic activation, in several strains of S. typhimurium (C3076, D3052, TA92, TA97, TA98, TA100, TA102, TA1000, TA1530, TA1531, TA1532, TA1535, TA1537, TA1538, TA1964 and TM677) (Green, 1975;McCann et al, 1975;Dorange et al, 1977;Wislocki et al, 1977;Green & Savage, 1978;Simmon, 1979a;Swanson et al, 1979;Cheh et al, 1980;Eder et al, 1980Eder et al, , 1982aEder et al, , 1982bBaker & Bonin, 1981, 1985Brooks & Dean, 1981;Garner et al, 1981;Gatehouse, 1981;Gocke et al, 1981;Hubbard et al, 1981;Ichinotsubo et al, 1981a;MacDonald, 1981;Nagao & Takahashi, 1981;Probst et al, 1981;Richold & Jones, 1981;Rowland & Severn, 1981;Simmon & Shepherd, 1981;Skopek et al, 1981;Sekizawa & Shibamoto, 1982;Suter & Jaeger, 1982;To et al, 1982aTo et al, , 1982bLiber, 1985;Matsushima et al, 1985;Rexroat & Probst, 1985;Zeiger & Haworth, 1985;Nakamura et al, 1987;Müller et al, 1993). A common observation in the majority of these tests was the cytotoxicity ...…”