Lack of Carcinogenic Effects of Isonicotinic Acid Hydrazide in the Syrian Golden Hamsters

Investigatin on the Tumor Producing Effect of Isonicotinic Acid Hydrazide in ASW/Sn Mice and MRC Rats

Administration of 0.1% isonicotinic acid hydrazide in drinking water to 9 week old ASW/Sn mice and to 5 week old MRC rats for the remainder of their lifetime resulted in an enhanced incidence of pulmonary tumors in the former species. It rose from 34 to 68% in the females as compared with the controls, while in the males, the treatment did not affect the development of these lesions nor did it increase the incidences of other types of tumors. In rats, the compound was also without any apparent carcinogenic effect.

The possible role of this chemical in tumorigenesis is discussed in light of the obtained results.

The mutagenicity of isoniazid in Salmonella and its effects on DNA repair and synthesis in human fibroblasts

A commercial sample of the tuberculostatic drug isoniazid (INH) was found to have a weak mutagenic activity towards Salmonella typhimurium strains TA100 and TA1535. The addition of a rat or mouse liver homogenate to the test system decreased the mutagenic effect of INH. Hydrazine, an impurity of the INH sample, was also weakly mutagenic in strains TA100 and TA1535, but not in the extent that could account for the mutagenicity of the INH sample. An inhibition of DNA synthesis in human fibroblasts was observed for INH, this effect being potentiated by the addition of manganese to the test system. There was no induction of unscheduled DNA synthesis in human cells by INH except in the presence of manganese.