A wealth of studies performed with a spectrum of methods spanning simple clearance
studies to the molecular identification of ion transporters has increased our understanding of
how approximately 1. 7 kg of NaCI and 180 L of H 2 O are absorbed by renal tubules in man
and how the urinary excretion is fine-tuned to meet homeostatic requirements. This review
will summarize our current understanding. In the proximal nephron, approximately 60 to
70% of the filtered Na+ and H 2 O is absorbed together with approximately 90% of the …