Intestinal absorption of several beta-lactam antibiotics. IV. Binding to the various components in the intestinal mucosa of rat and role in absorption process.

The binding characteristics of zwitterionic and monobasic beta-lactam antibiotics to the components in the intestinal mucosa of rat was investigated. From the binding experiments using the brush border membrane preparation and the insoluble cellular fractions, there was no correlation between the binding behavior and the absorption characteristics. However, there was a highly significant correlation between the affinity to the soluble F1 fraction and the absorption characteristics of these antibiotics. It was also found that the binding of these antibiotics to the other soluble protein fractions were significantly smaller than that to F1 fraction. It was postulated that the binding properties of these antibiotics to soluble F1 fraction play an important role in the absorption process.