Control of fluid transport in human rectal adenocarcinoma cells (hra-19) in monolayer and collagen gel cultures

HRA-19a1.1. cells, derived from a primary human rectal adenocarcinoma, form polarised monolayers when grown on tissue-culture plastic. HRA-19 monolayers have a heterogeneous morphology even after 150 passages in vitro or single cell cloning. The morphological changes observed in HRA-19 monolayers were postulated to be the result of vectorial fluid transport leading to accumulation of fluid between cells. To test this hypothesis, a variety of agents that control ion transport in colorectal epithelium were tested for their effect on HRA-19 morphology. Forskolin, cholera toxin and prostaglandin E2 all markedly changed HRA-19 monolayer morphology, with the rapid disappearance of intercellular spaces. These agents all stimulate Cl− secretion in colorectal epithelium, i.e. transport from basolateral to apical surface, and therefore would be expected to reduce fluid accumulation at the basolateral side of the cell. Conversely, vasopressin, which stimulates absorption of Na+ and water across colorectal epithelium, leads to a small increase in intercellular spaces in the monolayer. In collagen gel cultures, addition of cholera toxin, forskolin or prostaglandin E2 resulted in a large increase in colony size. In such treated cultures, thecolonies were ‘bubble-like’, often composed of a single rim of flattened cells, which appeared to encompass a fluid-filled space. Similar morphological changes were observed when HRA-19 cells were co-cultured with 3T3 cells. This effect was probably due, at least in part, to prostaglandin production by the 3T3 cells, as the effect could be markedly reduced by the addition of indomethacin to these cultures. These results strongly suggest that the morphological changes observed in HRA-19 monolayers are generated as cells change their fluid transport characteristics. Therefore, it would appear that vectorial fluid transport can lead to marked morphological changes in monolayer cultures, which differ from the more usually reported dome formation. In addition, these studies show that HRA-19 cells, derived from a primary human rectal adenocarcinoma, retain the ability to respond to many of the agents active in controlling transport in normal colorectal epithelium.