The effect of pyriproxyfen on the motoric activity of rat intestine - In vitro study.

The application of pyriproxyfen (PPF) to drinking water and constant exposure of the whole population to this insecticide is an unprecedented action on a world scale and presents a new and serious challenge for toxicology. The aim of the study was to evaluate the potential effect of PPF on the intestine muscle activity. The experiments were performed on isolated duodenum and jejunum strips of rat, in isometric conditions. Doses of PPF in the range of 0.032-100 μM were used in the experiments. The obtained results indicate that PPF affected significantly the spontaneous activity of duodenum and jejunum strips, PPF caused the muscle relaxation when used in the concentration of 0.8 μM and higher. The reaction to acetylcholine (ACh) when PPF preceded or followed ACh application was also reduced. It is demonstrated that the reduction of the contraction caused by ACh was stronger when duodenum strips were preincubated in the presence of PPF solution than in case of ACh-precontracted strips. The first significant reaction of duodenal strips appeared in the presence of PPF in a dose of 0.16 μM and 0.8 μM when the insecticide application preceded and followed ACh treatment, respectively. Besides, the duodenum turned out to be much more susceptible to the tested insecticide than jejunum. Taking into account PPF kinetic data obtained in animals, the observed disturbances were caused by the insecticide used in relatively high concentrations. However, the full risk estimation requires the kinetic data obtained in human, especially from monitoring studies on general population after long-term exposure to PPF.