passages.id: split_8_test_2347_passage
passages.type: progene_text
passages.text: In conclusion , our studies demonstrate that alterations of Ca2 + in levels , e.g. , by Ca2+ channel blockers , affect pH regulatory systems , such as apical Na + and H + exchange , and thereby alter the H + gradient that serves as the driving force for uptake of beta-lactams into intestinal epithelial cells .