The Hershberger Bioassay in Rats

1. The OECD initiated a high-priority activity in 1998 to revise existing guidelines and to 5 develop new guidelines for the screening and testing of potential endocrine disrupters (1). One 6 element of the activity was to develop a test guideline for the rat Hershberger Bioassay. After 7 several decades of use by the pharmaceutical industry, this assay was first validated by an 8 official expert committee in 1962 as a screening tool for androgenic chemicals (2). Over the last 9 five years, the rat Hershberger Bioassay has undergone an extensive validation program 10 including the compilation of a detailed methods paper (3), dissection guide and the conduct of 11 extensive intraand interlaboratory studies to show the reliability and reproducibility of the 12 bioassay with a potent reference androgen (testosterone propionate (TP)), two potent synthetic 13 androgens (trenbolone acetate and methyl testosterone), a potent antiandrogenic pharmaceutical 14 (flutamide), a potent inhibitor of a natural androgen (dihydrotestosterone-DHT) synthesis 15 (finasteride), several weakly antiandrogenic pesticides (linuron, vinclozolin, procymidone, p,p’ 16 DDT), a potent 5 alpha reductase inhibitor (finasteride) and two known negative chemicals 17 (dinitrophenol and nonylphenol (4)(5)(6)(7)(8). This Test Guideline XXX is the outcome of the 18 long historical experience with the bioassay and the experience gained during the validation test 19 programme and the results obtained thereby. 20 21