Heterogeneities in ICC Ca2+ Activity Within Canine Large Intestine

Abstract

Background & Aims In human and canine colon, both slow (slow waves, 2–8/min) and fast (myenteric potential oscillations; MPOs, 16–20/min) electrical rhythms in the smooth muscle originate at the submucosal and myenteric borders, respectively. We used Ca2+ imaging to investigate whether ICC at these borders generated distinct rhythms. Methods Segments of canine colon were pinned submucosal or myenteric surface uppermost, or cut in cross-section. Tissues were loaded with a Ca2+ indicator (fluo-4) and activity was monitored at 36.5±0.5°C using a CCD camera. Results Rhythmic, biphasic Ca2+ transients (5–8/min), similar in waveform to electrical slow waves, propagated without decrement as a wave front through the ICC-SM network (2–5mm/s), decaying exponentially through the thickness of the CM. In contrast, rhythmic intracellular Ca2+ waves (~16/min) and spontaneous reductions in Ca2+ were observed in ICC-MY. Normally, intracellular Ca2+ waves were unsynchronized between adjacent ICC-MY, although excitatory nerve activity synchronized activity. In addition, spontaneous reductions in Ca2+ were observed that inhibited Ca2+ waves. L-NA (100µM; NO antagonist) blocked the reductions in Ca2+ and increased the frequency (~19/min) of intracellular Ca2+ waves within ICC-MY. Conclusions ICC-SM form a tightly coupled network that is able to generate and propagate slow waves. In contrast, Ca2+ transients in ICC-MY, which are normally not synchronized, have a similar duration and frequency as MPOs. Like MPOs, their activity is inhibited by nitrergic nerves and synchronized by excitatory nerves.

Electrical slow waves in the mouse oviduct are dependent on extracellular and intracellular calcium sources

“…The amplitude of the average Ca 2ϩ transient of the second wave was reduced compared with the initial wave. The relationship between frequency and amplitude of Ca 2ϩ waves is similar to what has been described in the colon (32) and is likely the result of the time needed to refill intracellular Ca 2ϩ stores. The velocity of propagating Ca 2ϩ waves averaged of 2.7 Ϯ 0.27 mm/s (n ϭ 19).…”

Fat deposition in the tunica muscularis and decrease of interstitial cells of Cajal and nNOS-positive neuronal cells in the aged rat colon

“…The decrease of ICC, as observed in several motility disorders (13,17,21,24,25,34), reduces amplitudes of slow wave and, consequently, induces intestinal dysmotility by reducing electrical drive to smooth muscle contractions and peristalsis (38). A recent study has shown that the number and volume of ICC networks in the normal human stomach and colon declined with age using IHC analysis, but related molecular analysis, such as Western immunoblotting or real-time PCR, was absent in that study (15).…”

Ultrastructure of Interstitial Cells in Subserosa of Human Colon

“…The study of the electrophysiology of human colonic muscle is obviously in its infancy. In contrast with subserous ICC in mouse, guinea pig, canine, and nonhuman primate colon [Toma et al, 1999;Vanderwinden et al, 2000b;Aranishi et al, 2009;Lee et al, 2009;Chan et al, 2010;Han et al, 2010;Blair et al, 2012a], but in accordance with subserous interstitial cells in mouse internal anal sphincter [Cobine et al, 2011], IC-SS of the human colon are apparently Kit negative [He et al, 2000;Pieri et al, 2008;Liu et al, 2012]. ICC in murine, nonhuman primate, and human GI tracts express ANO 1, a Ca ++ -activated Cl -channel which is encoded by the transmembrane protein Tmem 16a [Gomez-Pinilla et al, 2009;Hwang et al, 2009;Kashyap et al, 2011;Sanders et al, 2011;Blair et al, 2012b].…”

“…In mouse colon we previously described c-kit-positive subserous ICC with an ultrastructure similar to colonic ICC at the myenteric plexus [Vanderwinden et al, 2000b], and a similar cell type may be present in guinea pig colon [Toma et al, 1999;Aranishi et al, 2009] as well as in canine colon [Lee et al, 2009]. The latter study on canine colon may have provided the first clue to a function of these cells, since it appeared that Ca ++ waves where initiated in subserous ICC and propagated towards ICC at the myenteric level through longitudinal muscle.…”