Adenosine accumulation as an indicator of cell-specific toxicity in rat lung slices

We have investigated the potential of adenosine uptake as a marker of chemically induced, cell-selective pulmonary injury using cell-selective toxicants. The administration of alpha-naphthylthiourea (ANTU), an agent which is known to damage the pulmonary endothelium, diminished spermidine and adenosine accumulation. In contrast, paraquat (a toxicant that selectively damages pulmonary epithelial cells) did not reduce adenosine uptake, although uptake of spermidine (a marker of pulmonary epithelial damage) was reduced. Taken together, these findings suggest that adenosine and spermidine are accumulated into different cell types. We characterized adenosine uptake and fate in rat lung slices. Accumulation was time and concentration dependent. In our experiments, the radiolabel retained within the slice comprised mainly nucleotides, primarily ATP. Adenosine-induced ATP elevation was initially a rapid event which reached a maximum. The use of a well characterized enzymatic assay for ATP confirmed the ATP elevation suggested by thin-layer chromatography (TLC). Adenosine uptake proved a more consistent marker of ANTU-induced pulmonary injury than measurement of 5-hydroxytryptamine (5-HT) uptake, which was slightly increased by ANTU administration to rats compared with control animals.