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

Abstract
The binding characteristics of zwitterionic and monobasic .beta.-lactam antibiotics [ampicillin anhydrous, cyclacillin anhydrous, amoxicillin trihydrate, cephalexin monohydrate, sodium cephaloridine, sodium cephalothin, cephradine dihydrate, and cefazolin] 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. There was a highly significant correlation between the affinity to the soluble F1 fraction and the absorption characteristics of these antibiotics. The binding of these antibiotics to the other soluble protein fractions were significantly smaller than that to F1 fraction. The binding properties of these antibiotics to soluble F1 fraction may play an important role in the absorption process.