Peroxide-induced effects on spontaneous contraction of murine small intestine: Lack of inhibition by antioxidants

An experimental model of inflammatory reaction in murine small intestine was developed by characterizing the effects of oxidative stress on spontaneous contractions in vitro. The tissue specimen were obtained from wild type mice (C57Bl6) and mounted in an organ bath allowing the registration of contraction forces under isometric conditions (Merkel, Thesis, 2010). Rhythmic spontaneous contractions were observed under normal perfusion conditions with a frequency (F) of approx. 20 ± 3/min and a mean amplitude (A) of 1.8 ± 0.4 mN. In order to induce oxidative stress, hydrogen peroxide was applied (0.05 – 0.6 mM/l) and the effects on contractile behaviour were recorded. Besides a longer lasting, yet transient, increase in contraction force (T), a slow reduction of the spontaneous contractions was found leading to decreased values of F and A, depending on the duration of the application. When, within one hour, the perfusion medium of the organ bath was changed again to normal conditions, all the contractile parameters returned to the initial values which lasted approx. 30 min. Therefore, at the one hand, the parameters of T, A and F, as well as the time needed for significant peroxide-induced changes on A and F can be used to quantify effects related to oxidative stress. On the other hand, they can also be used to recognize protection e.g. by antioxidants applied also to the tissue. Till now, we tested various substances among them vitamin C, rosmarinic acid, trolox and a herbal extract from Melissae folium, all of which were shown to exhibit strong antioxidative properties in different in vitro test systems (Germann et al, 2006). However, none of these revealed any significant protective effect on the changes in contractility, even when applied by preincubation prior to the peroxide.

Conclusion: Peroxide induced effects on murine intestinale spontaneous contractility, (contraction force and frequency) are described, which are very similar to those reported from rat gut (Gonzales & Sarna, 2000) and which can be reversed by peroxide free incubation of the tissue. Interestingly, different types of antioxidants could not interfere with or protect from these actions.