A new rat type I-like alveolar epithelial cell line R3/1: bleomycin effects on caveolin expression.

The study of function and regulation of the phenotype of alveolar type I (AT I) epithelial cells is limited by the rareness of suitable cell lines or primary cultures of this cell type. We describe in the present study the type I-like rat epithelial cell line R3/1. This cell line displays in vitro a phenotype with several characteristic features of AT I cells. R3/1 cells were analysed for mRNA and protein content of markers related to the AT I cell type (T1alpha, ICAM-1, connexin-43, caveolins-1 and -2) and AT II phenotypes [surfactant proteins (SPs) A, B, C and D]. The mRNAs for SPs were found to be at a low level. Moderate protein levels for SP-A and SP-B were found, and SP-C and SP-D proteins were not detectable. R3/1 cells are positive for CD44s, E-cadherin, cytokeratin, vimentin and RAGE, and bind the lectins BPA and SBA. For demonstration of the suitability of R3/1 cells for in vitro studies on epithelial injury, the cells were treated with bleomycin. As shown by real-time RT-PCR and immunoblotting, bleomycin-treatment of R3/1 cells resulted in a decrease in mRNA and protein for both caveolin-1 and caveolin-2 in comparison with controls. The AT I-like cell line R3/1 may serve as a promising tool for the study of lung cell biology.