DISSCUTION

Because the ultimate aim of anticancer treatment is to kill only the cancer cells, the therapeutic efficiency of anticancer agents could be increased by specificity and selectivity to cancer cells. Current understanding of anticancer strategy has led to attempts to screen for agents that selectively increase in cancer cells or to use apoptosis pathways specific for tumor cells. Therefore, our current findings suggested that the gastric proton pump inhibitor PPZ has very considerable advantages as anticancer treatment based on the following novel findings. First, PPZ selectively induced apoptosis in cancer cells, and this PPZ-induced apoptosis may be caused by suppressing ERK phosphorylation. This H⁺/K⁺-ATPase inhibitor sitmultaneously stimulated phosphorylation of p38 as well as deactivation of ERK in a dose- and time-dependent manner only in cancer cells. The different regulation of the individual MAPK subfamily by the proton pump inhibitor seems to be better considered as anticancer agents with high selectivity to cancer, because generally p38 is involved on apoptosis and stress signaling pathway, whereas ERK is activated by stimuli of cell growth and differentiation. Second, noncancer cells have mechanisms to counteract the PPZ-induced apoptosis by the induction of antiapoptotic molecules HSP70 and HSP27. We observed that PPZ-induced significant amounts of HSP70 much more than GGA, an agent generally known to induce HSP70 as a key action. Thus, the H⁺/K⁺-ATPase inhibitor may act to selectively induce apoptotic cell death in cancer cells without having any significantly adverse effects on the surrounding noncancer cells, and the feature of this agent contributes to safety in an aspect of clinical application. Third, PPZ would be selectively conversion of

the active form under the hypoxic and acidic condition, resulting in induction of significant apoptosis. Just like in the canaliculi of parietal cell, pH of inner space of the tumor was reported to be below 6.8 (Frenzel et al, 1994; Gillies et al, 1994). The finding shown in Fig.

2 showed that with lower pH of media, higher activities of apoptosis were observed. In all, these results suggest that PPZ can be used clinically as an anticancer agent.

One of the well-known properties of cancer cells is aerobic glycolysis, which may cause tumor acidification (Warburg et al, 1930; Holm et al, 1995; Vaupel et al, 1989). The cancer cell will take in glucose and form lactic acid, which will largely dissociate into the lactate ion and proton (H⁺). The lactate ion and H⁺ produced from the glycolysis are effluxed into the extracellular fluid leading to low extracellular pH and high intracellular pH of cancer. There are some mechanisms involved in the regulation of tumor pH; the main mechanism by which proton (H⁺) is exported is by the sodium-hydrogen antiport, using the energy of the Na⁺ gradient (Karamazyn et al, 1999; Wakabayashi et al, 1997). Tumor cells may possess an additional mechanism for H⁺ export via a vacuolar H⁺-ATPase (V-ATPase) of plasma membrane, the bicarbonate transporter, and the proton-lactate synporter (Maritinez-Z et al, 1993; Finbow et al, 1997). In the present study, we used the H⁺/K⁺-ATPase inhibitor for blocking the H⁺ export of tumor cells. The H⁺/K⁺-ATPase inhibitor successfully suppressed tumor cell viability by inducing apoptotic cell death. Thus, these findings implicate that blockage of another kind of proton pump predominantly expressed in tumor cells could be used as a promising anticancer drug.

Several inhibitors have been found to interact with vacuolar-type H⁺-ATPase, interfering with both ATP hydrolysis and proton translocation activities (Bowman et al,

1988; Zhang et al, 1992; Dross et al, 1993). Theses inhibitors can divided largely into two classes: inhibitors acting at a soluble cytoplasmic domain (N-ethylmaleimide and 4-nitrobenzo-2-oxa-1,3-diazole chloride) and inhibitors acting at transmembrane sites (dicyclohexyl-carbodimide, Bafilomycina A1, and Concanamycin A). Several research groups have already reported that these inhibitors of vacuolar-type H⁺-ATPase can induce apoptotic cell death in several human cancer cell lines including pancreatic cancer, hepatocellular carcinoma, and B-cell hybridoma cells (Nishihara et al, 1995; Ishisaki et al, 1999; Ohta et al, 1998; Aiko et al, 2002; Hasimoto et al, 2002). They also proved the involvement of cytochrome C release and caspase activation in vascuolar-type H⁺-ATPase inhibitor-induced apoptosis. The specific inhibitors of mammalian vacuolar-type H⁺-ATPase belonging to the benzolactone enamide class, such as salicylihalamide, lobatamides, and oximidines, were developed and appear promising as anticancer agents (Erickson et al, 1997;

Boyd et al, 2001). However, some reports are contradicting the proapoptotic effect of the proton pump inhibitor, suggesting that the inhibitor of mitochondria F0F1-ATPase proton pump, oligomycin, prevented apoptotic cell death (Schwerdt ea al, 2003; Matsuyama et al, 1998; Shchepina et al, 2002). .

However, there remain two limitations for anticancer application of a vascuolar-type H⁺-ATPase inhibitor like concanamycin A or bafilomycin A. The first one is nonselectivity of apoptosis of vascuolar-type H⁺-ATPase inhibitor, and the second problem is that the vacuolar-type H⁺-ATPase gene is considered a “housekeeping gene” expressed indiscriminately on every cell (Torigoe et al, 2002). Hence, there might be similar cytotoxicity provoked by current cytotoxic anticancer drugs. The feasibility of clinical

application of these factors is difficult despite strong apoptotic-inducing capability. On the other hand, PPZ showed selective induction of apoptosis in cancer cells. It rendered noncancerous cells escaping from apoptotic activities through the induction of antiapoptotic signaling molecules. Moreover, the fact the proton pump inhibitor is a prodrug requiring protonation after administration brings more hope that protonation is more easily performed within tumor tissues.

In conclusion, our findings provide novel mechanistic insight into the anticancer target of gastric proton pump, H⁺/K⁺-ATPase, and expand the repertoire of clinical use of gastric proton pump inhibitor as an anticancer drug by implicating the selective induction of apoptosis in cancer cells.

After H.pylori infection, the signal transduction enzymes, MAPK ERK1/2 and NFκB, are activation and these molecules are responsible for transcriptional activation of angiogenic growth factors, including IL-8, HIF-1α, and VEGF. Increase in H.pylori induced angiogenic factors stimulates the recruitment and activation of endothelial cells in the gastric mucosa, resulting in significant neovascularisation of the gastric mucosal layer which can provide a vulnerable and fertile environment for carcinogenesis. Chronic gastric inflammation triggered by H.pylori infection may predispose to the development and progression of gastric cancer. H.pylori induced angiogenesis might contribute to this H.pylori associated gastric carcinogenesis along with other carcinogenic events. In this study, for the first time, we have documented the mechanistic link between H.pylori infection and carcinogenesis, and the inhibitory effects of PPIs on H.pylori induced angiogenesis. PPI treatment efficiently inhibited IL-8, VEGF, and HIF-1α expression in H.pylori infected gastric epithelial cells,

which was due to inactivation of MAPK signaling induced by H.pylori infection. Thus these findings have helped shed light on antiangiogenic treatment with PPIs, drugs popularly prescribed for gastro-oesophageal acid related diseases and H.pylori eradiation. PPI therapy could be a promising protective therapeutic approach for H.pylori associated carcinogenesis.

Neovascularisation, the development of new blood vessels from existing endothelial precursors, is a general physiological mechanism critically involved in the normal repair process and in the pathogenesis of inflammatory and ulcerative epithelial lesions as well as malignant tumour growth, and even tumour metastasis (Jordan et al, 2004; Blagosklonny et al, 2004). Among the proangiogenic factors known, VEGF response one of the most potent stimuli of neoangiogenesis. Although previous studies found that enhanced VEGF gene expression contributed to the healing of peptic lesions in the stomach (Baatar et al, 2002;

Jones et al, 2001), here we demonstrated that H.pylori infection stimulation of blood vessels in the mucosa layer, which might be positive associated with propagation of gastric inflammantion as well as gastric carcinogenesis after H.pylori infection. Several investigations suggested that H.pylori infection stimulates host VEGF-A gene expression and H.pylori induced angiogenesis may play a critical role in the development of gastric cancer (Takahashi et al, 1996; Maeda et al, 1999; Kanai et al, 1998). Gastric adenocarcinomas frequently showed high levels of VEGF expression (Takahashi et al, 1996; Maeda et al, 1999), and neutralization of circulating VEGF with specific VEGF antibodies potently reduced the growth of gastric cancer (Kanai et al, 1998). Potent stimulators of angiogenesis related to H.pylori infection, H.pylori VacA toxin (Caputo et al, 2003), reactive oxygen species synthesized from neutrophils or macrophages (Park et al, 2003), CagA pathogenicity

islands (Cox et al, 2001; Innocenti et al, 2002), and lipopolysaccharide have been reported, and several pathways linking the bacterium to host angiogenesis have been revealed. A wider spectrum of genes induced by H.pylori in gastric epithelium was identified by high throughput analysis of cDNA microarray analysis, and most of these genes are responsible for angiogenesis and tumour invasion stimuli, such as ADAM series, IL-8, VEGF, integrins, VCAM-1, ICAM-1, E-selectin, GRO-α, and IL-6 (Cox et al, 2001; Innocenti et al, 2002).

The PPI PPZ, a substituted 2-pyridyl methyl/sulfinyl benzimidazole derivative, is a prodrug requiring protonation under acidic conditions for functions activation, accumulates selectively in the acidic gastric luminal space, and ultimately inhibits acid secretion by covalent binding with cysteins residues on the α-subunit of H⁺/K⁺-ATPase. These PPIs have been universally used with antibodies for the eradication of H.pylori and several types of acid related diseases, including gastro-oesophageal reflux diseases, peptic ulcer diseases, and Zollinger-Ellison syndrome (Sachs et al, 1997; Fitton et al, 1996). Increased gastric pH by PPIs stimulates resting H.pylori to activate metabolically and thus H.pylori are more susceptible to antibiotics (Iwahi et al, 1991; Nakao et al, 1998; Hirai et al, 1995; Tsuchiya et al, 1995; McGowan et al, 1994; Mauch et al, 1993). Apart from enhancing the susceptibility of H.pylori to antibiotics, we found, for the first time, that PPIs can directly influence host angiogenesis induced by H.pylori. Previously, we reported that PPIs had a strong inhibitory effect on phosphorylation of MAPK ERK1/2 and its administration showed anticancer activity in the xenograft nude mice model (Yeo et al, 2004). These inhibitory actions of the drug against ERK phosphorylation also involved suppression of H.pylori induced host angiogenesis. Blocking of H⁺ by PPIs caused an increase in extracellular pH (gastric lumen)

and a decrease in intracellular pH. The increased pH of the extracellular space may improve the hypoxic microenvironment surrounding gastric epithelial cells and interrupt H.pylori induced intracellular signaling via inhibition of MAPK activation. Compared with inhibitors of ERK1/2 or p38, PPZ showed stronger inhibitory activities than these (fig. 14), in a dose dependent manner. However, the influence of this drug on NFκB transcriptional activation was minor (fig. 14).

In conclusion, we have shown that considerable angiogenic activities were stimulated in the gastric mucosa after H.pylori infection, for which increasing proangiogenic growth factors from gastric epithelial cells were responsible. PPIs could have significant inhibitory activities against H.pylori associated angiogenesis. Therefore, the current data indicate that as H.pylori infection causally promoted host angiogenesis, which has been attributed to either augmented inflammation or enhanced carcinogenesis, PPIs could be potentially used for inhibition of H.pylori provoked angiogenesis.

REFERENCES

1. Aiko K, Tsujisawa T, Koseki T. Involvement of cytochrome c and caspases in apoptotic cell death of human submandibular gland ductal cells induced by concanamycin A. Cell Signalling 14:717-722, 2002

2. Allen LA. Modulating phagocyte activation : the pros and cons of Helicobacter pylori virulence factors. J Exp Med 191:1451-1454, 2000

3. Baatar D, Jones MK, Tsugawa K. Esophageal ulceration triggers expression of hypoxia-inducible factor-1 alpha and activates vascular endothelial growth factor gene : implications for angiogenesis and ulcer healing. Am J Pathol 161:1449-1457, 2002

4. Bagchi D, Bhattacharya G, Stohs SJ. Production of reactive oxygen species by gastric cells in association with Helicobactor pylori. Free Radic Res 24:439-450, 1996

5. Ballif BA, Blenis J. Molecular mechanisms mediating mammalian mitogen-activated protein (MAPK) kinase (MEK)-MAPK cell survival signals. Cell Growth Differ 12:397-408, 2001

6. Betten A, Bylund J, Cristophe T. A proinflammatory peptide from Helicobacter pylori

activates monocytes to induce lymphocyte dysfunction and apoptosis. J Clin Invert 108:1221-1228, 2001

7. Beere HM, Wolf BB, Chain K, Cohen GM, Green D. Heat shock protein 70 inhibits apoptosis by preventing recruitment of procaspase-9 to the Apaf-1 apoptosome. Nat Cell Biol 2:469-475, 2001

8. Besancon M, Shin JM, Mercier F. Membrane topology and omeprazole labeling of the gastric H⁺,K⁺-adenosinetriphosphatase. Biochemistry 32:2345-2355, 1993

9. Blagosklonny MV. Antiangiogenic therapy and tumor progression. Cancer Cell 5:13-17, 2004

10. Bowman EJ, Siebers A, Altendorf K. Bafilomycin : a class of inhibitors of membrane ATPase from microorganisms, animal cells, and plant cells. Proc Natl Acad Sci USA 85:7972-7976, 1988

11. Boyd MR, Farina C, Belfiore P. Discovery of a novel antitumor benzolactone enamide class that selectively inhibits mammalian vascuolar-type (H⁺)-atpases. J Phamacol Exp Ther 297:114-120, 2001

12. Bruey JM, Ducasse C, Bonniaud P, Ravagnan L, Susin SA, Diaz-Latoud C. HSP27 negatively regulates cell death by interacting with cytochrome C. Nat Cell Bio 2:645-652, 2000

13. Buzzard KA, Giaccia AJ, Killender M. Heat shock protein 72 modulates pathways of stress-induced apoptosis. J Biol Chem 273:17147-17153, 1998

14. Caputo R, Tuccillo C, Manzo BA. Helicobacter pylori VacA toxin up-regulates vascular endothelial growth factor expression in MKN 28 gastric cells through an epidemal growth factor receptor-, cyclooxygenase-2-dependent mechanism. Clin Cancer Res 9:2015-2021, 2003

15. Cox JM, Clayton CL, Tomita T. cDNA array analysis of cag pathogenicity island-associated Helicobacter pylori epithelial cell response genes. Infect Immun 69:6970-6980, 2001

16. Crawford HC, Krishna US, Israel DA. Helicobacter pylori strain-selective induction of matrix metalloproteinase-7 in vitro and within gastric mucosa. Gastroenterology 125:1126-1136, 2003

17. Dent P, Jarvis WD, Birrer MJ. The roles of signaling by the p42/p44 mitogen-activated protein (MAP) kinase pathway; a potential route to radio- and chemo-sensitization of tumor cells resulting in the induction of apoptosis and loss of clonogenicity. Leukemia 12:1843-1850, 1998

18. Dixon MF, Gental RM, Yardley JH. Classification and grading of gastritis, the updated Sydney system. Am J Surg Pathol 20:1161-1181, 1996

19. Dross S, Bindseil KU, Bowman EJ, Siebers A, Zeek A, Altendrof K. Inhibitory effect of modified bafilimycins and concanamycins on P- and V- type adenosinetriphosphatases.

Biochemistry 32:3902-3906, 1993

20. Erickson KL, Beutler JA, Cardellina II, Boyd MR. Salicylihalamides A and B, Novel Cytotoxic Macrolides from the Marine Sponge Haliclona sp. J Org Chem 62, 1997

21. Ethridge RT, Hellmich MR, Dobois RN, Evers BM. Inhibition of heat-shock protein 70 induction in intestinal cell overexpressing cyclooxygenase 2. 115:1454-1463, 1998

22. Finbow ME, Harrison MA. The vacuolar H⁺-ATPase: A universal proton pump of eukaryotes. Biochem J 324:697-712, 1997

23. Fitton A, Wiseman L. Pantoprazole, A review of its pharmacological properties and therapeutic use in acid-related disorders. Drugs 51:460-482, 1996

24. Franceschi F, Genta RM, Gasbarrini A. Helicobacter pylori infection and expression of the angiogenic factor platelet-derived endothelial cell growth factor by pre-neoplastic gastric mucosal lesions and gastric carcinoma. Dig Liver Dis 34:621-625, 2002

25. Franklin RA, McCubrey JA. Kinases : positive and negative regulators of apoptosis.

Leukemia 14:2019-2034, 2000

26. Frenzel T, Kohler S, Bauer H, Niedballa U, WeinMann HJ. Non-invasive in vivo measurement using a fluorinated pH probe and fluorine-19 magnetic resonance spectroscopy.

Invest Radiol 29:S220-222, 1994

27. Garrido C, Gurbuxani S, Ravagnan L, Kroemer G. Heat shock proteins : endogenous modulators of apoptotic cell death. Biochem Biophys Res Commun 286:433-442, 2001

28. Garrido C, Bruey JM, Fromentin A, Hamman A, Arrigo AP, Solary E. HSP27 inhibits cytochrome c-dependent activation of procaspase-9. FASEB J 13:2061-2070, 1999

29. Gillies RJ, Liu Z, Bhujwall Z. PMBS measurements of extracellular pH of tumor using 3-aminopropylphosphonate. Am J Physiol 267:C195-203, 1994

30. Gupta RA, Polk DB, Krishna U. Activation of peroxisome proliferators-activated receptor gamma suppresses nuclear factor kappa B-mediated apoptosis induced by Helicobacter pylori in gastric epithelial cells. J Biol Chem 276:31059-66, 2001

31. Hasimoto S, Ishiki A, Yamato K, Ailo K, Amagasa T, Nishihara T. Intracellular apoptosis-inducing factor is induces by vacuolar H⁺-ATPase inhibitor in B lineage cells.

J of Cellular Physiology 186:65-72, 2002

32. Helmlinger G, Yuan F, Dellian M, Jain RK. Interstitial pH and pO2 gradients in solid tumor in vivo: high resolution measurements reveal a lack of correlation. Nat Med 3:177-182, 1997

33. Hirai M, Azuma T, Ito S. A proton pump inhibitor, E2810, has antibacterial activity through binding to Helicobacter pylori. J Gastroenterol 30:461-464, 1995

34. Holm E, Hagmuller E, Staedt U. Substrate balances across colonic carcinomas in humans.

Cancer Res 55:1373-1378, 1995

35. Horn J. The proton pump inhibitors: similarities and differences. Clin Ther 22:266-280, 2000

36. Innocenti M, Thoreson AC, Ferrero RL. Helicobacter pylori-induced activation of human endothelial cells. Infect Immun 70:4581-4590, 2002

37. Ishisaki A, Hashimoto S, Amagasa T, Nishihara T. Caspase-3 activation during the process of apoptosis induced by a vacuolar type H(+)-ATPase inhibitor. Biol Cell 91:507-513, 1999

38. Iwahi T, Satoh H, Nakao M. Lansoprazole, a novel benzimidazole proton pump inhibitor, and its related compounds have selective activity against Helicobacter pylori. Antimicrib Agents Chemother 35:490-496, 1991

39. Jaffe EA, Nachman RL, Becker CG. Culture of human endothelial cells derived from umbilical veins. Identification by morphologic and immunologic criteria. J Clin Invert 52:2745-2756, 1973

40. Johnson GL, Lapadat R. Mitogen-activated protein kinase pathways mediated by ERK, JNK, and p38 protein kinases. Science 298:1911-1912, 2002

41. Jones MK, Kawanaka H, Baatar D. Gene therapy for gastric ulcers with single local injection of naked DNA encoding VEGF and angiopoietin-1. Gastroenterology 121:1040-1047, 2001

42. Jordan MA, Wilson L. Microtubules as a target for anticancer drugs. Nat Rev Cancer 4:253-265, 2004

43. Kanai T, Konno H, Tanaka T. Anti-tumor and anti-metastatic effects of human-vascular – endothelial-growth-factor-neutralizing antibody on human colon and gastric carcinoma xenotransplanted orthotopically into nude mice. Int J Cancer 77:933-936, 1998

44. Karamazyn M, Gan XT, Humpheys RA, Yoshisa H, Kusumoto K. The myocardial Na⁺ -H⁺ exchange: structure, regulation, and its role in heart desease. Circ Res 85:777-786, 1999

45. Kitadai Y, Sasaki A, Ito M. Helicobacter pylori infection influences expression of genes related to angiogenesis and invasion in human gastric carcinoma cells. Biochem Biophys Res Commun 311:809-814, 2003

46. Lee AH, Tannock IF. Heterogeneity of intracellular pH and of mechanisms that regulate

intracellular pH in populations of culture cells. Cancer Res 58:1901-1908, 1998

47. Maeda S, Yoshida H, Mitsuno Y. Analysis of apoptotic and antiapoptotic signaling pathways induced by Helicobacter pylori. Gut 50:771-778, 2002

48. Maeda K, Kang SM, Onoda N. Vascular endothelial growth factor expression in preoperative biopsy specimens correlates with diseases recurrence in patients with early gastric carcinoma. Cancer 86:566-571, 1999

49. Mauch F, Bode G, Malfettheiner P. Identification and characterization of an ATPase system of Helicobacter pylori and the effect of proton pump inhibitors. Am J Gastroenterol 88:1801-1802, 1993

50. Maritinez-Zaguilan R, Lynch RM, Maritinez GM, Gillies RJ. Vacuolar-type H⁺ ATPase are functionally expressed in plasma membranes of human tumor cells. Am J Physiol 265: C1015-29, 1993

51. Mccoy CL, Parkins CS, Chaplin DJ, Griffiths JR, Rodrigus LM, Stubbs M. The effect of blood flow modification on intra- and extracellular pH measured by ³¹P MRS in murine tumors. Br J Cancer 72:905-911, 1995

52. Matsuyama S, Xu Q, Velours J, Reed JC. The mitochondrial F0F1-ATPase proton pump is required for function of the proapoptotic protein Bax in yeast and mammalian cells.

Mol Cell 1:327-336, 1998

53. McGowan CC, Cover TL, Blaser MJ. The proton pump inhibitor omeprazole inhibits acid survival of Helicobacter pylori by a urease-independent mechanism.

Gastroenterology 107:1573-1578, 1994

54. Mehlen P, Kretz-Remy C, Preville X, Arrigo AP. Human hsp27, Drosophila hsp27 and human alpa B-crystallin expression-mediated increase in glutathione is essential for the protective activity of these proteins against TNFalpha-induced cell death. EMBO J 15:2695-2706, 1996

55. Mosser DD, Caron AW, Bourget L, Denis Larose C, Massie B. Role of human heat shock protein 70 in protection against stress-induced apoptosis. Mol Cell Biol 17:5317-5327, 1997

56. Nakao M, Malifetheiner P. Growth inhibitory and bactericidal activites of lansoprazole compared with those of omeprazole and pantoprazole against Helicobacter pylori.

Helicobacter 3:21-27, 1998

57. Namkung W, Lee JA, Ahn W. Ca2 activates cystic fibrosis transmembrane conductance regulator- and Cl- -dependent HCO3 transport in pancreatic duct cells. J Bio Chem 278:200-207, 2003

58. Nelson N. Evolution of organellar proton-ATPase. Biochim Biophys Acta 1100:109-124, 1992

59. Nishihara T, Akifusa S, Koseki T, Kato S, Muro M, Hanada N. Specific inhibitors of vacuolar type H (+)-ATPase induce apoptotic cell death. Biochem Biophys Res Commun 212:255-262, 1995

60. Ohta T, Arakawa H, Futagami F. Bafilomycin A1 induces apoptosis in the human pancreatic cancer cell line Capan-1. J Pathol 185:324-330, 1998

61. Park JH, Kim TY, Jong HS. Gastric epithelial reative oxygen species prevent normoxic degradation of hypoxia-inducible factor-1 alpha in gastric cancer cells. Clin Cancer Res 9:433-440, 2003

62. Peek RM Jr, Blasre MJ. Helicobacter pylori and gastrointestinal tract adenocarcinomas.

Nat Rev Cancer 2:28-37, 2002

63. Pouyet B, Piloquet P, Vo NH, Pardal G, Lefrane G. Ultrastructural and cytochemical analysis of Na⁺, K⁺-ATPase in parietal cells of gastric mucosa in the rabbit.

Histochemistry 97:255-261, 1992

64. Rokutan K. Gastric mucosal protection and cell proliferation: role of heat shock proteins in gastric mucosal protection. J Gast Hepatology 15:D12-19, 2000

65. Sachs G. Proton pump inhibitors and acid-related diseases. Phamacotherapy 17:22-37, 1997

66. Sachs G, Shin JM, Briving C, Wallmark B, HerseyS. The pharmacology of the gastric acid pump: the H⁺,K⁺-ATPase. Am Rev Pharmacol Toxicol 35:277-305, 1995

67. Scott DR, Helander HF, Hersey SJ, Sachs G. The site of acid secretion in the mammalian parietal cell. Biochem Biophys Acta Biomembr 1146:73-80, 1993

67. Scott DR, Helander HF, Hersey SJ, Sachs G. The site of acid secretion in the mammalian parietal cell. Biochem Biophys Acta Biomembr 1146:73-80, 1993