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  • Title: Organic cation transport in rabbit alveolar epithelial cell monolayers.
    Author: Shen J, Elbert KJ, Yamashita F, Lehr CM, Kim KJ, Lee VH.
    Journal: Pharm Res; 1999 Aug; 16(8):1280-7. PubMed ID: 10468032.
    Abstract:
    PURPOSE: To characterize organic cation (OC) transport in primary cultured rabbit alveolar epithelial cell monolayers, using [14C]-guanidine as a model substrate. METHODS: Type II alveolar epithelial cells from the rabbit lung were isolated by elastase digestion and cultured on permeable filters precoated with fibronectin and collagen. Uptake and transport studies of [14C]-guanidine were conducted in cell monolayers of 5 to 6 days in culture. RESULTS: The cultured alveolar epithelial cell monolayers exhibited the characteristics of a tight barrier. [14C]-Guanidine uptake was temperature dependent, saturable, and inhibited by OC compounds such as amiloride, cimetidine, clonidine, procainamide, propranolol, tetraethylammonium, and verapamil. Apical guanidine uptake (Km = 129 +/- 41 microM, Vmax = 718 +/- 72 pmol/mg protein/5 min) was kinetically different from basolateral uptake (Km = 580 +/- 125 microM, Vmax = 1,600 +/- 160 pmol/mg protein/5 min). [14C]-Guanidine transport across the alveolar epithelial cell monolayer in the apical to basolateral direction revealed a permeability coefficient (Papp) of (7.3 +/- 0.4) x 10(-7) cm/sec, about seven times higher than that for the paracellular marker [14C]-mannitol. CONCLUSIONS: Our findings are consistent with the existence of carrier-mediated OC transport in cultured rabbit alveolar epithelial cells.
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