Characterisation of Rat Alveolar Cell Line R3/1

The rat cell line R3/1 displays several phenotypical features of alveolar epithelial type I cells. In order to characterise the cell line as an in vitro model for drug disposition studies, R3/1 cells were cultured on Transwell filters and the transepithelial electrical resistance (TEER) was measured as a parameter for the integrity of cell layers. Presence of cell junctional proteins (i.e., E-cadherin, occludin, ZO-1 and ZO-2) was studied on mRNA (by reverse transcriptase-polymerase chain reaction, RT-PCR) and antigen level (by immunofluorescence microscopy, IFM). Moreover, the expression pattern of catabolic peptidases (carboxypeptidase M, aminopeptidases A, B, N and P, γ-glutamyltransferase, dipeptidylpeptidase IV, angiotensin-converting enzyme, and endopeptidases 24.11 and 24.15) was analysed in R3/1 cells and compared to rat alveolar epithelial I-like cells in primary culture. TEER values were peaking at ~99±17 Ω cm2 after 5 days in culture. Addition of 0.1 µM dexamethasone together with foetal bovine serum at 20% increased TEER by 65%. However, none of culture conditions used in our study yielded monolayers with TEER values comparable to those of primary cultures of rat pneumocytes. RT-PCR revealed the absence of transcripts encoding for E- cadherin and occludin. However, ZO-1 and -2 mRNA transcripts..