Carbon dioxide mediates duodenal mucosal alkaline secretion in response to luminal acidity in the anesthetized rat  Mathias Holm*, Berndt Johansson*, Anders Pettersson‡, Lars Fändriks§  Gastroenterology  Volume 115, Issue 3, Pages 680-685 (September 1998) DOI: 10.1016/S0016-5085(98)70147-7 Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 1 Effect of a 5-minute exposure to isotonic NaCl saturated with 100% CO2 (pH 4; ○), 0.1 mmol/L HCl (pH 4; ▵), and 10 mmol/L HCl (pH2; ♦) on duodenal mucosal alkaline secretion. Controls, subjected to sham stimulation (isotonic NaCl; ■), are included for comparison. Data are means ± SEM of six experiments in each group. Gastroenterology 1998 115, 680-685DOI: (10.1016/S0016-5085(98)70147-7) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 2 (A) Effect of a 5-minute exposure to isotonic NaCl saturated with 100% CO2 (pH 4) on duodenal mucosal alkaline secretion in controls, in the presence of intraluminally administered L-NAME (0.3 mmol/L), and in animals treated with 5 mg/kg indomethacin intravenously. (B) Effect of a 5-minute exposure to 10 mmol/L HCl (pH 2), made isotonic by NaCl, on duodenal mucosal alkaline secretion in controls, in the presence of intraluminally administered L-NAME (0.3 mmol/L), and in animals treated with 5 mg/kg indomethacin intravenously. Data shown are means ± SEM of the percent change from baseline to the highest value obtained within 20 minutes after exposure (n = 6 in each group). *P < 0.05, significant difference from untreated controls exposed to 100% CO2 or 10 mmol/L HCl, respectively; n.s., nonsignificant difference from controls. Gastroenterology 1998 115, 680-685DOI: (10.1016/S0016-5085(98)70147-7) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 2 (A) Effect of a 5-minute exposure to isotonic NaCl saturated with 100% CO2 (pH 4) on duodenal mucosal alkaline secretion in controls, in the presence of intraluminally administered L-NAME (0.3 mmol/L), and in animals treated with 5 mg/kg indomethacin intravenously. (B) Effect of a 5-minute exposure to 10 mmol/L HCl (pH 2), made isotonic by NaCl, on duodenal mucosal alkaline secretion in controls, in the presence of intraluminally administered L-NAME (0.3 mmol/L), and in animals treated with 5 mg/kg indomethacin intravenously. Data shown are means ± SEM of the percent change from baseline to the highest value obtained within 20 minutes after exposure (n = 6 in each group). *P < 0.05, significant difference from untreated controls exposed to 100% CO2 or 10 mmol/L HCl, respectively; n.s., nonsignificant difference from controls. Gastroenterology 1998 115, 680-685DOI: (10.1016/S0016-5085(98)70147-7) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 3 Time course of the effect of a 5-minute exposure to NaCl saturated with 100% CO2 (pH 4) on duodenal mucosal alkaline secretion in the presence of intraluminally administered L-NAME (0.3 mmol/L) and in animals treated with 5 mg/kg indomethacin intravenously. Data are means ± SEM of six experiments in each group. Gastroenterology 1998 115, 680-685DOI: (10.1016/S0016-5085(98)70147-7) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 4 Effect of a 5-minute exposure to isotonic solutions initially containing 150 mmol/L NaCl (pH 5.9, PCO2 0 mm Hg [sham stimulation]), 25 mmol/L NaHCO3 and 5 mmol/L HCl (pH 6.8, PCO2 120 mm Hg), 25 mmol/L NaHCO3 and 10 mmol/L HCl (pH 6.4, PCO2 240 mm Hg), and 25 mmol/L NaHCO3 and 20 mmol/L HCl (pH 5.6; PCO2 480 mm Hg) on duodenal mucosal alkaline secretion. Data are means ± SEM of the percent change from baseline to the highest value obtained within 20 minutes after exposure (n = 6 in each group). *P < 0.05, significant difference from sham-stimulated controls; n.s., nonsignificant difference from controls. Gastroenterology 1998 115, 680-685DOI: (10.1016/S0016-5085(98)70147-7) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 5 Effect of a 5-minute exposure to an isotonic solution initially containing 25 mmol/L NaHCO3 and 10 mmol/L HCl (pH 6.4; PCO2 240 mm Hg) on duodenal mucosal alkaline secretion in the presence of intraluminally administered L-NAME (0.3 mmol/L) and in the presence of D-NAME (0.3 mmol/L), the inactive stereoisomer of L-NAME. Data are means ± SEM of six experiments in each group. Gastroenterology 1998 115, 680-685DOI: (10.1016/S0016-5085(98)70147-7) Copyright © 1998 American Gastroenterological Association Terms and Conditions