抄録
Absorption mechanism of four water-soluble dyes, methylene blue (MB), bromthymol blue (BTB), bromphenol blue (BPB), and phenol red (PR), from the rat small intestine was investigated. Absorptive characteristics of these dyes, highly ionized compounds of very low lipoid solubilities at physiological pH range of the small intestine, varied widely. The percentage net absorption of MB, BTB, BPB, and PR were 46.0±2.9, 14.7±3.7, 2.4±1.1, and 1.2±0.5%, respectively. The degree of binding to the intestinal mucosa preparation determined in vitro was correlated to the disappearance from the intestinal lumen and the accumulation in tissue rather than net absorption. The binding to brush borders, the first step of intestinal absorption, was paralleled to the tendency of uptake by isolated epithelial cells. These results suggest that binding to the mucosa, especially to the brush borders (microvilli) as the first step, is important in the process of absorption of these water-soluble dyes from the rat small intestine. The poor absorbability of PR is due to its very low affinity to the intestinal mucosa in addition to poor lipoid solubility.
