This dataset consists of 33 raw MS files, an associated peak list and result file, acquired on an Q Exactive plus mass spectrometer operated in Data Dependent Acquisition mode. The files are associated with a manuscript submitted for publication. Publication title: " Expression of transport proteins in the rete mirabile of European silver and yellow eel " The swimbladder rete mirabile is known for its highly efficient countercurrent concentrating ability, allowing for the generation of hyperbaric oxygen partial pressures in the range of several 10th or even more than 100 atmospheres. The transcapillary exchange between venous and arterial capillaries is often explained by passive diffusion and hydraulic (osmotic) transport. The reported countercurrent concentration of lactate ions, however, raises the possibility that specific transport proteins contribute to the countercurrent concentrating ability of the rete. We therefore analyzed the transcriptome as well as the proteome of rete capillaries of the European eel. The results clearly show the presence of a large number of membrane transport proteins in the transcriptome as well as in the proteome. ATP required to energize ion and metabolite transport can be generated in the aerobic metabolism. A high ROS defense capacity is established in rete endothelial cells, probably connected to the hyperbaric oxygen partial pressures, generated in the rete by back-diffusion of oxygen.