Effects of short-term administration of maleic hydrazide or hydrazine on rat hepatic microsomal enzymes

The herbicide maleic hydrazide (MH), in amounts greatly exceeding its residue level in foods, had no apparent effect on the hepatic microsomal enzyme system of Fischer rats. In vivo, up to 1 g/kg of MH did not affect hexobarbital sleep times (HST) and in vitro, 2 g/kg of the sodium salt of MH altered neither the metabolism of benzo(a)pyrene and aniline nor the activities of cytochrome b 5 and P-450. Hydrazine-SO 4, a frequent contaminant of commercial MH preparations, in moderately high doses prolonged HST and diversely altered metabolism in vitro. The effects of hydrazine impurities, if present, could be significant in toxicity tests where excessive doses of MH are administered.