Volume 120, Issue 6, Pages 1430-1437 (May 2001) Increased calcium influx is responsible for the sustained mechanical tone in colon from dystrophic (mdx) mice  Flavia Mulè  Gastroenterology  Volume 120, Issue 6, Pages 1430-1437 (May 2001) DOI: 10.1053/gast.2001.24054 Copyright © 2001 American Gastroenterological Association Terms and Conditions

Fig. 1 Typical tracings showing the development of active tone only in the isolated colonic segments from dystrophic mouse. Gastroenterology 2001 120, 1430-1437DOI: (10.1053/gast.2001.24054) Copyright © 2001 American Gastroenterological Association Terms and Conditions

Fig. 2 Time-dependent effects of Ca2+-free Krebs on the amplitude of the spontaneous contractions in colonic segments from control or mdx mice. (A) Typical intraluminal pressure recordings before and 5 and 15 minutes after omission of Ca2+ from external solution. (B) Graphical representation of the mean amplitude of spontaneous contractions measured at different times. The contractions of normal colon were abolished within 15 minutes, and those of mdx colon were abolished within 25 minutes. Data are expressed as a percentage of the amplitude of the spontaneous contractions. All values are means ± SEM of 7 experiments. Gastroenterology 2001 120, 1430-1437DOI: (10.1053/gast.2001.24054) Copyright © 2001 American Gastroenterological Association Terms and Conditions

Fig. 3 Inhibitory effects of nifedipine on the spontaneous contractions of colonic segments from control or mdx mice. (A) Typical intraluminal pressure recordings before and after administration of nifedipine (0.1 μmol/L). (B) Graphical representation of the mean amplitude of spontaneous contractions measured in the presence of the different concentrations of nifedipine. The amplitude of the spontaneous contractions before addition of nifedipine was taken as 100%. The decrease in the amplitude of contractions of colon from mdx mice was significantly greater than that of control animals at every concentration of nifedipine, except at 1 μmol/L, which abolished all phasic activity. All values are means ± SEM of 6 experiments. *P < 0.05. Gastroenterology 2001 120, 1430-1437DOI: (10.1053/gast.2001.24054) Copyright © 2001 American Gastroenterological Association Terms and Conditions

Fig. 4 Effects of nifedipine and/or Ca2+-free Krebs on the spontaneous tone of colonic segments from mdx mice. Nifedipine as well as omission of Ca2+ from extracellular medium reduced the mechanical tone. Nifedipine and Ca2+-free Krebs did not cause any additive effects. All values are means ± SEM of 5–7 experiments. Gastroenterology 2001 120, 1430-1437DOI: (10.1053/gast.2001.24054) Copyright © 2001 American Gastroenterological Association Terms and Conditions

Fig. 5 Time course of the effect of CPA (10 μmol/L) on the amplitude of spontaneous contractions of colonic segments from control or mdx mice. (A) Typical intraluminal pressure recordings before and after 20 minutes of CPA administration. (B) Graphical representation of the mean amplitude of spontaneous contractions measured at different times from the beginning of perfusion with CPA. After an early increase in amplitude of the pressure waves in both preparations, CPA abolished the contractions only in the control preparations. All values are means ± SEM of 5 experiments and are expressed as percentages of the amplitude of the spontaneous contractions. Gastroenterology 2001 120, 1430-1437DOI: (10.1053/gast.2001.24054) Copyright © 2001 American Gastroenterological Association Terms and Conditions

Fig. 6 Effects of CPA on the contraction induced by carbachol (10 μmol/L) in colon from control or mdx mice. (A) Typical tracings showing the effect of carbachol in different experimental conditions. Arrowheads indicate carbachol application. (B) Graphical representation of the mean amplitude of contractions induced by carbachol in different experimental conditions. Original refers to the contraction in normal Krebs. Release refers to the first contraction induced by carbachol (10 μmol/L) in Ca2+-free solution and is indicative of the carbachol-releasable intracellular calcium store. The release contraction of mdx colon was significantly greater (P < 0.01) than that of control, suggesting that a larger intracellular calcium store exists in mdx colon. Repletion refers to the carbachol-induced contraction after tissues previously depleted of calcium were allowed to replete intracellular calcium stores for 30 minutes in normal Krebs without or with CPA (10 μmol/L). The repletion contraction was recorded in Ca2+-free solution and thus is caused by intracellular release of calcium. There was no significant difference (P > 0.05) in the repletion contraction between control and mdx colon. The presence of CPA during the 30-minute repletion period significantly reduced the ability of both control and mdx colon to replete calcium stores. All values are means ± SEM of 6 experiments and are expressed as percentages of the contraction induced by carbachol (10 μmol/L) in normal Krebs. The effect of carbachol was measured as maximum contraction. *Significantly different from original contraction. **Significantly different from release contraction of mdx colon. ***Significantly different from the repletion contraction. Gastroenterology 2001 120, 1430-1437DOI: (10.1053/gast.2001.24054) Copyright © 2001 American Gastroenterological Association Terms and Conditions