The approach taken and conclusions reached by the Joint FAO-WHO Expert Committee on Food Additives

Transcription

1 The approach taken and conclusions reached by the Joint FAO-WHO Expert Committee on Food Additives Fxr Van Leeuwen To cite this version: Fxr Van Leeuwen. The approach taken and conclusions reached by the Joint FAO-WHO Expert Committee on Food Additives. Annales de Recherches Vétérinaires, INRA Editions, 1991, 22 (3), pp <hal > HAL Id: hal Submitted on 1 Jan 1991 HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

2 The approach taken and conclusions reached by the Joint FAO-WHO Expert Committee on Food Additives FXR van Leeuwen Rijksinstituut voor Volksgezondheit den Milieuhygiene, Antonie van Leeuwenhoeklaan 9, PO Box Y, 3720 BA Bilthoven, The Netherlands (27-28 March 1990: International Meeting on Anabolics, Toulouse France) Summary &horbar; The synthetic anabolic steroid trenbolone acetate (TBA) was evaluated by the Joint FAO-WHO Expert Committee on Food Additives (JECFA) in 1981, 1982, 1987 and Effects on reproductive function in rats were observed, with no-effect level of 0.5 mg TBA/kg diet. No evidence was found for a teratogenic potential of TBA in rats. From the results of in vitro as well as in vivo mutagenicity assays it was concluded that TBA was probably not genotoxic and that the increased tumour incidence observed in long-term studies in mice and rats arose as a consequence of the hormonal activity of TBA. The concentration of sex hormones in the circulation was significantly reduced and histopathological abnormalities (particularly in testes, ovaries and uteri) were observed in male and female pigs fed with high doses of TBA. The marginal no-effect level for these effects was 0.1 mg/kg diet, equal to 2 wg/kg bw. The 34th JECFA meeting established = an acceptable daily intake of yg/kg bw of TBA. trenbolone acetate / reproduction / teratogenicity / mutagenicity I hormonal activity Résumé &horbar; Approche adoptée et conclusions obtenues par le comité d experts sur les additifs alimentaires FAO-OMS. L acétate de trenbolone (hormone stéroïde de synthèse à activité anabolisante) a été évalué en 1981, 1982, 1987 et 1989 par le comité d experts sur les additifs alimentaires FAO-OMS. Des effets sur les fonctions de reproduction du rat ont été observés chez les animaux nourris avec des hautes doses de trenbolone. La dose sans effet était de 0,5 mg T8Alkg d aliment. Aucune preuve du potentiel tératogène de l acétate de trenbolone n a été fournie chez le rat D après les résultats des tests de mutagénicité, il a été conclu que l acétate de trenbolone n était probablement pas génotoxique et que l augmentation de l incidence des tumeurs observée dans les études à long terme chez la souris et le rat était due à l activité hormonale de la trenbolone. Les concentrations sériques des hormones sexuelles étaient significativement réduites et des troubles histopathologiques (en particulier dans les testicules, les ovaires et les utérus) étaient observés chez des porcs mâles et femelles nourris avec des doses élevées de trenbolone. La dose sans effet était 0,1 mglkg d aliment, équivalent à 20 pglkg de poids corporel. La 34e réunion du comité d experts sur les additifs alimentaires a fixé à 0-0, 02 gglkg de poids corporel la dose journalière acceptable de ce composé. acétate de trenbolone / reproduction / tératogénicité / mutagénicité / activité hormonale

3 The synthetic anabolic steroid, trenbolone acetate (TBA), was evaluated by the Joint FAO-WHO Expert Committee on Food Additives (JECFA) at the 26th meeting in 1981, the 27th meeting in 1982, the 32nd meeting in 1987 and finally at the 34th meeting in 1989 (WHO, 1988, 1989). The available toxicological information comprised data on metabolism, reproduction, teratogenicity, mutagenicity and carcinogenicity of TBA, and additional data on the mutagenic and hormonal activity of the primary hydrolisation and the major metabolite a-tboh. Various experiments have been performed to assess the effects of TBA on reproductive function. In multigeneration reproduction studies rats were exposed to dietary concentrations varying from mg TBA/kg diet. Effects on litter size, pup weight, pup mortality and testis weight of the offspring were observed at the highest dose-levels. No effect on reproductive function was observed at 0.5 mg/kg diet, equivalent to a dose of 30 pg/kg body weight (bw). In teratogenicity studies with rats no evidence was found for a teratogenic potential of TBA. With respect to the safety evaluation of TBA the results of long-term carcinogenicity studies in mice and rats are of major importance. Mice fed a diet containing TBA concentrations equal to 0.005, 0.1, 0.9 or 9 mg/kg bw showed an increased incidence of liver tumours in the 2 highestdose groups of males and the high-dose females. In rats, only the high-dose (1.9 mg/kg bw) females showed a slight but significant increase in pancreatic islet cell tumours (benign and malignant combined). In order to distinguish between genotoxic or hormonal activity as the underlying mechanism for the observed tumour induction, a comprehensive set of mutagenicity data for TBA, a- and (3-TBOH was evaluated at the 32nd JECFA meeting. All tests were negative with the exception of a mutation assay in mouse lymphoma cells and micronucleous induction in Chinese hamster ovary cells, both showing equivocal results. Furthermore, equivocal results were obtained with (3-TBOH in cell transformation assays with Syrian hamster embryo fibroblasts and mouse C3H10T1/2 cells. It was recognized by the JECFA that the relation between effects in transformation assays and a possible genotoxic activity is still unclear. In the case of trenbolone, interpretation of test results was further hampered by an inverse dose relationship in some cases. At its 34th meeting, the JEC- FA evaluated additional information with respect to the possible genotoxicity of a- and (3-TBOH (Lutz et al, 1988; Schiffmann et al, 1988). In in vitro assays a weak binding of (3-TBOH to DNA isolated from S typhimurium and to calf thymus DNA was found. In the latter case this binding was reduced by the addition of active and inactivated S9. In vivo [3-TBOH showed a weak binding potential to rat liver DNA with a relatively low covalent binding index, comparable with results evaluated earlier by the JEFCA. In an additional mutagenicity test [3- TBOH caused a slight but consistent doserelated increase in the number of revertants in S typhimurium TA-100. This increase, which is within the range of % revertants as found in all other tests, was not recognized as a positive result. However, the question of whether the criterion of a doubling in the number of spontaneous revertants is generally applicable may be raised, particularly in the case of compounds which exert bactericidal activity. With respect to cell transformation, earlier results in Syrian hamster embryo fibroblasts were confirmed. Both a- and (3- TBOH induced morphological transforma-

4 tion. The (3-TBHO-transformed but not the a-tboh transformed cells showed neoplastic potential after subcutaneous injection in thymus-aplastic nude mice. With the former compound, fibrosarcomas developed at the site of injection. No transformation however, either for a- or for 0-TBOH, was found in mouse C3H10T1/2 cells. A similar pattern was observed for the induction of micronuclei. Both compounds showed a positive effect in Syrian hamster embryo cells but were negative in mouse C3H10T1/2 cells. Taking into account the existing difficulty in interpreting the results of transformation assays and the impressive amount of genotoxicity data, schematically summarized in table I, the 34th JEC- FA meeting concluded &dquo;that it was unlikely that TBA was genotoxic&dquo;. Consequently it reconfirmed its earlier-expressed opinion that the increased tumour incidence ob- studies in mice and served in long-term rats arose as a consequence of the hormonal activity of TBA. It was therefore decided to base the toxicological evaluation of TBA and its metabolites on their nohormonal effect level. On an earlier occasion, the JECFA had already evaluated data with respect to the hormonal activity of TBA and a- and p- TBOH, comprising studies in castrated male rhesus macaque monkeys and in pigs. Since the castrated male monkey appeared to be highly sensitive to compounds with antigonadotropic activity, the no-effect level of 2 mg/kg bw for (3-TBOH observed in this test model is most relevant for the safety evaluation of trenbolone. Since no individual data on the pig studies were available at the 32nd meeting, the JECFA reevaluated this information, including requested data on the metabolite a-tboh during its last meeting (WHO, 1989). In castrated male pigs, interference with the rise in luteinizing hormone (LH) occurring after castration was taken as the relevant criterion. The previously established no-effect levels of 10 pg/kg bw for (3-TBOH and 100 pg/kg bw for a-tboh were confirmed. In Large White hybrid domestic pigs fed diets containing 0, 0.1, 2.0 or 20 mg/kg TBA for 14 wk, effects on gonad weight and the concentration of sex hormones in the circulation were observed. In males, testis weight was significantly decreased in the highest dose groups while a marginal effect was still observed at 0.1

5 mg/kg diet. In male pigs the concentration of testosterone and oestradiol was significantly reduced in the 2 highest-dose groups, with marginal effects at the lowestdose level. Serum progesterone was decreased at the 2 highest doses in female pigs. These changes were accompanied by histopathological abnormalities, particularly in testis, ovaries and uteri of pigs in the 2 highest dose groups. These data indicate a marginal no-hormonal effect level of TBA of 0.1 mg/kg diet, equal to = 2 gg/ kg bw. This value is in accordance with the nohormonal effect level of 2 pg/kg bw for P- TBOH as established in the castrated rhesus monkey. The 34th JECFA meeting therefore established an acceptable daily intake of pg/kg bw for TBA by applying a safety factor of 100 to the mentioned marginal no-effect level (WHO, 1989). For the toxicological evaluation of trenbolone, a threshold approach is taken based on the &dquo;unlike-liness&dquo; of a genotoxic potential. Although this appears a very reasonable approach, some doubt still exists with respect to possible genotoxic activity. Hopefully this round table meeting will provide us with more insight into the relevance of these recently obtained data, so that the &dquo;genotoxicity issue&dquo; as regards trenbolone can be solved once and for all. REFERENCES Lutz WK, Deuber R, Caviezel M, Sagelsdorff P, Friederich U, Schlatter C (1988) Trenbolone growth promotant: covalent DNA binding in rat liver and in Salmonella typhimurium and mutagenicity in the Ames test. Arch Toxicol 62, Schiffmann D, Hieber L, Schmuck G, Pechan R, Metzler M, Heuschler D (1988) Trenbolone induces micronucleus formation and neoplastic tranformation in Syrian hamster fibroblasts but not in mouse C3Hl 0Tl /2 cells. Arch Toxi- Co162, WHO (1988) Evaluation of Certain Veterinary Drug Residues in Food. 32nd Report, Joint FAO/WHO Expert Committee on Food Additives, 1988 Techn Rep Ser, 763, WHO Geneva WHO (1989) Evaluation of Certain Veterinary Drug Residues in Food. 34th Report, Joint FAO/WHO Expert Committee on Food Additives, 1989 Techn Rep Ser, 788, WHO Geneva