Eur J Pharmacol. 1993 Aug; 239(1-3): 241-3.

Conventionalization of germ-free rats reverses the disability of rhein anthrone to induce laxation.

Nijs G, De Witte P, Geboes K, Mertens J, Eyssen H.

Laboratory of Pharmaceutical Biology and Phytopharmacology, Institute of Pharmaceutical Sciences, K.U. Leuven, Belgium.

This study shows that rhein anthrone has no laxative potency in germ-free rats because after intracaecal administration of a dose of 50 mg/kg the large intestine transit exceeded 240 min. The time course of the laxative potency of rhein anthrone injected intracaecally was evaluated after peroral inoculation of germ-free rats with the caecal contents of conventional rats. Large intestine transit was measured at consecutive periods, on days 0, 1, 2, 3 and 5 after peroral inoculation. It appeared that 1 day after peroral inoculation the laxative potency of rhein anthrone was already established (large intestinal transit < 10 min) and laxation remained on the following days (days 2, 3 and 5). We concluded that rhein anthrone is inactive in germ-free rats and acquires laxative potency after peroral inoculation of germ-free rats with caecal contents of conventional rats.