Effect of taurine on the gastrointestinal absorption of drugs--ionic requirement for the action.

In order to resolve the mechanism of taurine-induced enhancement of drug absorption, the effect of ionic components of the luminal solutions on drug absorption was examined by using the loop of rat stomach in situ. K+ has its remarkable influence on the control values of aspirin absorption. The control values, at and above 25 mM already reached to a nearly corresponding degree as that of taurine-induced enhancement, resulting in apparent disappearance of enhancement effect. On the other hand, the action of taurine on salicylamide absorption is revealed to be K+ concentration-dependent, whereas all the control values remain fairly constant. Moreover, at the higher concentration of 10 mM, aspirin absorption turned out to be significantly inhibited in the presence of taurine, and this finding is supposed to be attributed to the protection of taurine against aspirin-induced gastric mucosal damage. On the contrary, salicylamide absorption was greatly enhanced. All these results clearly support that the mechanism of action of taurine toward both drugs should be separately considered.