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. 2010 Oct;24(10):3840-9.
doi: 10.1096/fj.10-156232. Epub 2010 Jun 11.

The transwall gradient across the mouse colonic circular muscle layer is carbon monoxide dependent

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The transwall gradient across the mouse colonic circular muscle layer is carbon monoxide dependent

L Sha et al. FASEB J. 2010 Oct.

Abstract

Gastric and small intestinal circular smooth muscle layers have a transwall resting membrane potential (RMP) gradient that is dependent on release of carbon monoxide (CO) from interstitial cells of Cajal (ICCs). Our aim was to determine whether a RMP gradient exists in the mouse colon and whether the gradient is CO dependent. Microelectrodes were used to record RMPs from muscle cells at different depths of the circular muscle layer from wild-type and heme oxygenase-2-knockout (HO-2-KO) mice. A transwall RMP gradient was present in wild-type mice. The CO scavenger oxyhemoglobin (20 μM) and the heme oxygenase inhibitor chromium mesoporphyrin IX (CrMP, 5 μM) abolished the transwall gradient. The gradient was absent in HO-2-KO mice. Tetrodotoxin (1 μM) caused a significant depolarization in circular smooth muscle cells throughout the circular muscle layer and abolished the transwall gradient. Removal of the submucosal neurons abolished the gradient. The majority of submucosal neurons contained HO-2 immunoreactivity (HO-2-IR), while ICCs did not. These data show for the first time that a transwall gradient exists across the circular smooth muscle layer of the mouse colon, that the gradient is due to CO, and that the source of CO is the submucosal neurons.

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Figures

Figure 1.
Figure 1.
RMP gradient across the circular muscle layer of the colon of WT mice. Left panel: each dot represents the RMP from a recorded cell; line is the regression for all cells from the same preparation. The x axis is the location (μm) of the cell relative to the submucosa; the y axis is the RMP from that cell. Right panel: regression lines for cells from all (n=11) recorded WT mouse colon preparations. Each dashed line is the regression line for an individual preparation. Thick solid line is the mean regression line for all preparations. Slope of the mean regression line was 0.6 ± 0.1 mV/10 μm. Data points are not shown in right panel.
Figure 2.
Figure 2.
Transwall gradient across the circular muscle layer in WT mouse colon was abolished by oxyhemoglobin, CrMP, and TTX, while l-NNA had no significant effect on the transwall gradient. Slope of the mean regression line in WT mouse colon preparations in the presence of oxyhemoglobin was −0.2 ± 0.1 mV/10 μm. Slopes of the mean regression line in WT mouse colon preparations in the presence of CrMP and in the presence of TTX were −0.01 ± 0.4 and 0.2 ± 0.2 mV/10 μm, respectively. Slopes in the treated preparations were not significantly different from 0 slope (P>0.05). Slope of the mean regression line in WT mouse colon preparations in the presence of l-NNA (0.6±0.1 mV/10 μm) was significantly different from 0 slope (P<0.01).
Figure 3.
Figure 3.
Transwall gradient was absent in HO-2-KO mice. Slope of the mean regression line in HO-2-KO mice (0.01±0.1 mV/10 μm) was not significantly different from 0 slope (P>0.01).
Figure 4.
Figure 4.
HO-2-IR was found in myenteric ganglia (A–C) and submucous ganglia (D–F) but was not found in cells that contained ACK2-IR (G–I) in colonic preparations. A) PGP 9.5 IR in a myenteric ganglion. B) HO-2-IR in the same ganglion as in A. C) Superimposed images from A and B. D) Submucous ganglion with PGP 9.5 IR. E) Same region with HO-2-IR. F) Superimposed images from D and E. G) ACK2-IR in the myenteric plexus region. H) Same region with HO-2-IR. I) Superimposed images from G and H. J) Submucosal border region with a PGP 9.5 IR containing submucous ganglion. K) Same region with HO-2-IR. L) Superimposed images from J and K. There were some single cells (arrows in J, K) that contained HO-2-IR.
Figure 5.
Figure 5.
Colocalization of HO-2-IR and ACK2-IR was found in jejunal preparations but not in colonic preparations. A) HO-2-IR (green) was colocalized with ACK2-IR (red) positive structures (arrow) in the myenteric plexus area of a jejunal preparation. B) ACK2-IR-positive ICCs of the submucosa and HO-2-IR-positive cells in submucosal area of a colonic preparation. There was no colocalization of HO-2-IR and ACK2-IR.
Figure 6.
Figure 6.
Removal of the submucosa abolished the transwall gradient in WT mice. Slope of mean regression line in WT mouse colon without the submucosa was 0.12 ± 0.08 mV/10 μm (n=9), which was not significantly different from 0 slope (P>0.05). Transwall gradient was still absent during repetitive EFS to enhance the activity of myenteric ganglion neurons. With repetitive EFS, slope of the mean regression line was −0.06 ± 0.07 mV/10 μm (n=4, P>0.05, compared to 0 slope).

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References

    1. Bauer A. J., Reed J. B., Sanders K. M. (1985) Slow wave heterogeneity within the circular muscle of the canine gastric antrum. J. Physiol. 366, 221–232 - PMC - PubMed
    1. Bauer A. J., Sanders K. M. (1985) Gradient in excitation-contraction coupling in canine gastric antral circular muscle. J. Physiol. 369, 283–294 - PMC - PubMed
    1. Hara Y., Kubota M., Szurszewski J. H. (1986) Electrophysiology of smooth muscle of the small intestine of some mammals. J. Physiol. 372, 501–520 - PMC - PubMed
    1. Liu L. W., Huizinga J. D. (1993) Electrical coupling of circular muscle to longitudinal muscle and interstitial cells of Cajal in canine colon. J. Physiol. 470, 445–461 - PMC - PubMed
    1. Smith T. K., Reed J. B., Sanders K. M. (1987) Interaction of two electrical pacemakers in muscularis of canine proximal colon. Am. J. Physiol. Cell Physiol. 252, C290–C299 - PubMed

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