PUTRESCINE UPTAKE BY ALVEOLAR EPITHELIAL-CELL MONOLAYERS EXHIBITING DIFFERING TRANSEPITHELIAL ELECTRICAL RESISTANCES

Rat alveolar type II cells were isolated following elastase digestion and cultured on polycarbonate filters at various densities and in diff erent media. Two days after seeding, the cells formed a monolayer on t he filters which consisted predominately of type II cells, these then de-differentiated to a alveolar type I-like cell monolayer by day 6. T he seeding density and media utilized affected the transepithelial ele ctrical resistance (TEER) generated by the monolayer. Only certain cul ture conditions allowed the production of a monolayer that mimics, put atively, the in vivo alveolar epithelium (TEER greater than 1000 Ohm c m(2)). V-max and K-m values for the uptake of putrescine by monolayers exhibiting low and high TEERs on day 6 were determined. The capacity of the putrescine uptake mechanisms was greater in cell monolayers exh ibiting a high TEER than those exhibiting a low TEER, suggesting that the TEER does not only measure the ''tightness'' of the monolayer but contains an element representative of the viability of the cell monola yer. The selection of appropriate TEERs for cell culture investigation s is discussed.