COMPARATIVE TOXICITY OF 2-HYDROXY-3-ALKYL-1,4-NAPHTHOQUINONES IN RATS

2-Hydroxy-1,4-naphthoquinone has previously been shown to cause severe haemolytic anaemia and renal tubular necrosis in animals. In order to establish if such toxic effects are common to other 2-hydroxynaphthoq uinone derivatives, the short-term, toxicity of a number of 2-hydroxy- 3-alkyl-1,4-naphthoquinones has been compared in rats. 2-Hydroxy-3-met hyl-, 2-hydroxy-3-ethyl- and 2-hydroxy-3-propyl-1,4-naphthoquinone wer e found to cause both haemolysis and renal damage, although the severi ty of the changes provoked by these substances was much lower than tho se induced by the parent compound at an equivalent dose-level. Further more, the toxicity of the hydroxy-alkylnaphthoquinones decreased with increasing size of the alkyl substituent and no toxic changes were rec orded in animals dosed with 2-hydroxy-3-butyl- or 2-hydroxy-3-pentyl-1 ,4-naphthoquinone. The relationship between the in vivo effects of the se substances and previously reported data on their in vitro cytotoxic ity is discussed in relation to the mechanism of toxicity of these and other naphthoquinone derivatives.