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Abstract
1. Pulmonary absorption studies in the rat showed that intratracheally administered 5–10 mM bromphenol blue, bromcresol green and bromthymol blue markedly increased the absorption rate of 0·1 mM phenol red.
2. Similarly, 1–10 mM bromphenol blue increased the absorption rate of 0·1 mM p-aminohippuric acid, tetraethylammonium and mannitol by 2- to 18-fold in a concentration-dependent manner.
3. Mannitol absorption was enhanced more by bromthymol blue, sulpho-bromophthalein, bromcresol purple, thymol blue and bromcresol green than by bromphenol blue or m-cresol purple. Chlorphenol red and phenol red had no effect on mannitol absorption.
4. The results indicated that certain sulphonic acid dyes increase the permeability of the respiratory tract epithelium, perhaps by increasing its porosity.