SLC9A1 and gastroesophageal reflux disease: On the contrary, based on the presence of NHE1 in the basolateral membrane of the esophageal epithelium (Shallat et al., 1995), Siddique and Khan (Siddique and Khan, 2003) argue that the protons extruded by NHE1 lead to a basolateral acidification of the extracellular space which could then cause tissue damage and eventually GERD.