Proximal Convoluted Tubule. The proximal convoluted tubule is the site where majority (65%) of ions and water in the urinary space is reabsorbed back into the body.The cells of the proximal convoluted tubule have a deeply stained, eosinophilic cytoplasm.roximal Convoluted Tubule. The proximal convoluted tubule is the site where majority (65%) of ions and water in the urinary space is reabsorbed back into the body.