Luciano L, Reale E, Rechkemmer G, von Engelhardt W
J Membr Biol. 1984;82(2):145-56. doi: 10.1007/BF01868939.
Absorption of short-chain fatty acids has been studied in the proximal and the distal colon of anaesthetized guinea pigs. Segments were perfused with a solution similar in chemical composition to that of normal colonic fluids. In the proximal colon the permeability of the mucosa was similar for acetate, propionate and butyrate. For acetate the permeability was significantly higher in the proximal than in the distal colon, and the reverse was seen for butyrate. In the distal colon the short-chain fatty acids seem to be absorbed mainly in the undissociated form due to their lipid solubility; a paracellular pathway for the dissociated molecules is of no major importance. In the proximal colon, on the other hand, a considerable portion of acetate and propionate disappears in the ionized form. Light microscopy (semithin sections) and electron microscopy (freeze-fracture replicas) showed remarkable morphological differences between the proximal and the distal colon. "Leaky spots" with only few strands were present in the zonulae occludentes between the epithelial cells at the surface of the proximal colon. In the distal colon the junctions between the cells were more compact, and significantly more strands separated the lumen from the intercellular space. These results suggest that short-chain fatty acids could be absorbed by a paracellular pathway in the proximal colon, and not in the distal colon. In the proximal colon the number of strands of the zonulae occludentes between surface cells and that between cryptal cells was similar. On the contrary, in the distal colon significantly more strands were present between surface cells than between cryptal cells. Morphological and physiological considerations suggest that absorption of short-chain fatty acids in the crypts is negligible.
已在麻醉豚鼠的近端结肠和远端结肠中研究了短链脂肪酸的吸收情况。用化学成分与正常结肠液相似的溶液灌注肠段。在近端结肠中，乙酸盐、丙酸盐和丁酸盐的黏膜通透性相似。对于乙酸盐，近端结肠的通透性显著高于远端结肠，而丁酸盐则相反。在远端结肠中，由于短链脂肪酸的脂溶性，它们似乎主要以未解离形式被吸收；解离分子的细胞旁途径并不重要。另一方面，在近端结肠中，相当一部分乙酸盐和丙酸盐以离子形式消失。光学显微镜（半薄切片）和电子显微镜（冷冻断裂复制品）显示近端结肠和远端结肠之间存在明显的形态学差异。近端结肠表面上皮细胞之间的紧密连接中存在仅有少量链的“渗漏点”。在远端结肠中，细胞间连接更紧密，将管腔与细胞间空间分隔开的链明显更多。这些结果表明，短链脂肪酸可能通过近端结肠的细胞旁途径被吸收，而不是在远端结肠。在近端结肠中，表面细胞之间和隐窝细胞之间紧密连接的链数量相似。相反，在远端结肠中，表面细胞之间的链明显多于隐窝细胞之间的链。形态学和生理学方面的考虑表明，隐窝中短链脂肪酸的吸收可忽略不计。
