Response of Smooth Muscle from Proximal and Distal Human Colon

Abstract

Regional differences in colonic motility may be responsible for the orderly transit of intraluminal contents through the colon. The aims of this study were to compare the effect of stretch on active and passive stress development in colonic muscle from the proximal and distal colon and to compare the responses of these tissues to KC1 or bethanechol stimulation. Strips of taenia or circular smooth muscle were obtained from the disease‐free segment of the colon removed for adenocarcinoma. Passive, active, and total isometric stress were measured on full‐thickness strips of circular or longitudinal taenial muscle stimulated with bethanechol (10−4 M) as the muscles were stretched to 120% of the length of optimum tension (Lo.) The tissues then were stimulated with increasing concentrations of KCI and bethanechol while being stretched at Lo. The active stress in the proximal circular muscle was greater at all levels of stretch than in distal circular or longitudinal muscle (p <.001). The resting and passive stress were greater in distal circular and longitudinal taenial muscle than in proximal circular muscle (p < .05). There was a dose‐dependent increase in stress development to bethanechol and KCl in each type of muscle. Proximal circular muscle had the greatest response. The EDSO was shifted to the right in distal circular muscle (2.6 ± 0.1 × 10−5 M) compared to proximal circular muscle (1.1 ± 0.1 × 10−5 M) (p < .001). These studies suggest that muscle stress differs in different locations of the colon and the role of active and passive stress development must be considered in models explaining in vivo colonic motility disturbances.

Myogenic regional responsiveness to cholinergic and vipergic stimulation in human colon

“…Segmental activity is a peculiarity of motor patterns of the ascending colon and the higher regional sensitivity observed on circular muscle strips to CCh in this region might likely contribute to this motor pattern, confirming previous observations in human colonic tissue 11,24 . However, similar to what was previously reported on rabbit colonic SMC, 8 the regional differences in sensitivity to CCh were lacking at the cellular level suggesting that, even if CCh acts directly on smooth muscle, the higher sensitivity observed in ascending colon strips needs to be ascribed to the non‐muscular component of the motor apparatus, which is activated in parallel to smooth muscle in the whole tissue.…”

Gender- and Age-Related Differences in Muscular and Nerve-Mediated Responses in Human Colon

“…Carbacholinduced contractions were measured as increases over baseline activity. Stress induced by carbachol or electrical stimulation was calculated as mN per cross-sectional area (expressed in cm 2 ) [11][12][13][14][15][16]. Concentration-response data were expressed as percentage of maximum response to carbachol and as the concentration of carbachol required to induce a 50% maximal response (EC 50 ).…”

“…In previous work, we showed that electrically evoked contractions of human colon circular muscle strips have two components, cholinergic and tachykininergic, the latter being sustained by NANC excitatory nerves. Full inhibition of electrically evoked contractions was achieved only with combined atropine and SR48968, NK 2 receptor antagonist [15]. This component is most probably expressed in elderly male patients.…”

Gender-differences of in vitro colonic motility after chemo- and radiotherapy in humans

“…The results are given as means ± standard error (SE) (n indicates the number of patients). Carbachol- and histamine-induced contractions were measured as increases over baseline activity and were calculated as mN per cross sectional area (expressed in cm 2 ) [ 18 , 19 , 22 , 23 ]. We then expressed concentration-response data as a percentage of the maximal response to carbachol or histamine and calculated half-maximal effective concentration (EC 50 ) values with 95% confidence intervals (CIs) from log concentration-response curves using non-linear regression analysis.…”

“…We then expressed concentration-response data as a percentage of the maximal response to carbachol or histamine and calculated half-maximal effective concentration (EC 50 ) values with 95% confidence intervals (CIs) from log concentration-response curves using non-linear regression analysis. Stress induced by electrical stimulation was expressed as mN per cross sectional area [ 18 , 19 , 22 , 23 ]. We compared data sets with a paired Wilcoxon test (responses before and after treatment), unpaired Mann-Whitney U test (differences between groups), and unpaired Student’s t test, as appropriate.…”