Inhibitory action of benzimidazole fungicides on the in vivo incorporation of [ 3H]thymidine in various organs of the mouse

Abstract

The effect of benomyl on the DNA turnover in various organs of the mouse was evaluated by measuring the incorporation of [ 3H]thymidine 24 hr after oral administration of different doses (1.3, 2.55 and 5.1 mmol/kg body weight) of benomyl. In the thymus, spleen and testis there was a clear relationship between dose and effect, the no-observed-effect level being 1.3 mmol/kg body weight. However, in the liver and kidney there was no obvious relationship between dose and effect, the [ 3H]thymidine incorporation being inhibited even at the lowest dose. Equimolar amounts of the closely related fungicide carbendazim inhibited the [ 3H]thymidine incorporation only in the testis. The observed difference between the two compounds was not a result of different absorption rates. Whole-body autoradiography indicated a rapid absorption and a similar distribution pattern for [phenyl(U)- 14C]benomyl and [phenyl(U)- 14C]carbendazim. Apart from an accumulation in the retina, liver and kidney, most other organs were almost devoid of [ 14C]benomyl- and [ 14C]carbendazim-associated radioactivity.