[Isolated smooth muscle cells of the human colon. Cytophysiological study]

Gross normal specimens of human distal colon were obtained at operation for cancer. Smooth muscle cells were separated from internal and external layers of the muscularis. They were dissociated by digestion with collagenase, isolated and concentrated by successive centrifugations. Colonic smooth muscle cell contraction was measured using various concentrations of carbamylcholine (10(-9) to 10(-4) M); relaxation was tested using atropine (10(-9) to 10(-4) M) on colonic smooth muscle cells pre-contracted by carbamylcholine. Compared with previous descriptions, human smooth muscle cells were smaller than in other species with an enlarged distribution of cell size (30 microns to 150 microns in length). Significant dose-response curves were obtained for both carbamylcholine and atropine. However, 3 original points characterized human colonic smooth muscle cells: a) the cells isolated from the internal layer were significantly more sensitive than those isolated from the external layer (10(-9) M vs 10(-7) M); b) for the muscle cells isolated from both the internal and external layers, small colonic smooth muscle cells were significantly more sensitive. On the other hand, these cells were shown to be located near conjunctive septae, and intramural plexuses; c) analysis of contraction curves demonstrated a more efficient response for colonic smooth muscle cells of the internal layer than for those of the external layer of the muscularis.