LONG-TERM TOXICITY CARCINOGENICITY STUDY OF L-HISTIDINE MONOHYDROCHLORIDE IN F344 RATS/

The long-term toxicity and carcinogenicity of histidine, an essential amino acid for most animal species, were examined in Fischer 344 (F344 ) rats. Groups of 50 males and 50 females were given L-histidine monoh ydrochloride (HMHC) in their diet at concentrations of 0 (control), 1. 25 and 2.5% for 104 wk; these dose levels were selected on the basis o f the results of a subchronic toxicity study, in which body weights we re depressed and formation of sperm granulomas in the epididymis was h istologically evident in males fed 5.0% HMHC. All surviving rats were killed at wk 107. Increases in red blood cell count, haemoglobin value and haematocrit level were observed in male rats given 2.5% HMHC. A v ariety of tumours developed in all groups, including the control group , but all the neoplastic lesions were histologically similar to those known to occur spontaneously in this strain of rats, and no statistica lly significant increase in the incidence of any tumour was found in t he treated groups of either sex. Thus, it was concluded that, under th e present experimental conditions, HMHC is not carcinogenic in F344 ra ts. Copyright (C) 1996 Elsevier Science Ltd.