Urodilatin is a natriuretic peptide isolated from human urine and belongs to the family of A type natriuretic peptides. Urodilatin is differentially processed to a peptide of 32aa from the same precursor as ANP. It is synthesized in kidney tubular cells and secreted luminally. After secretion from epithelial cells of the distal and/or connecting tubules, Urodilatin interacts downstream at distal segments of the nephron with luminally located receptors whereby it regulates Na(+) and water reabsorption. Thus, the physiological function of the renal Urodilatin system can be described as a paracrine intrarenal regulator for Na(+) and water homeostasis, considering Urodilatin as a real diuretic natriuretic regulatory peptide.