Microscope Imageof a Kidney (IMAGE) Max-Planck-Gesellschaft Caption This is a microscopic cross-section of a kidney. The image shows the organ's filtration tubes, the so-called tubules. The cell walls of the tubules contain proteins, which are active as water transporter (green) and sodium transporters (red). The cell nuclei are highlighted in blue. Credit MPI for Heart and Lung Research Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.