Basolateral Cl-/HCO3- exchange in epithelial cells from guinea pig distal colon.

In guinea pig distal colon, H+ secretion into the lumen due to the apical ouabain-sensitive H+, K(+)-ATPase activity is associated with HCO3- exit into the serosa. This study aimed at elucidating (1) the transport mechanism of HCO3- exit across the basolateral membrane and (2) the relation of lactate release to the H+, K(+)-ATPase activity, in isolated mucosae mounted in Ussing chamber. The HCO3- exist across the basolateral membrane depended on the serosal Cl-. 4,4'-Diisothiocyanostilbene- anostilbene-2,2'-disulfonic acid (DIDS) applied to the serosal side reduced the rate of HCO3- exit across the basolateral membrane. The lactate was released to the serosal side, but not to the luminal side. The serosal lactate appearance was abolished when the apical H+, K(+)-ATPase was inhibited by luminal ouabain. These results suggest that HCO3- exit across the basolateral membrane is mediated by a DIDS-sensitive Cl-/HCO3- exchange. In addition, the lactic acid production appears to be coupled to the apical H+, K(+)-ATPase activity.