Members of all four families of ectonucleotidases, namely ectonucleoside triphosphate diphosphohydrolases (NTPDases), ectonucleotide
pyrophosphatase/phosphodiesterases (NPPs), ecto-5′-nucleotidase and alkaline phosphatases, have been identified in the renal
vasculature and/or tubular structures. In rats and mice, NTPDase1, which hydrolyses ATP through to AMP, is prominent throughout
most of the renal vasculature and is also present in the thin ascending limb of Henle and medullary collecting duct. NTPDase2
and NTPDase3, which both prefer ATP over ADP as a substrate, are found in most nephron segments beyond the proximal tubule.
NPPs catalyse not only the hydrolysis of ATP and ADP, but also of diadenosine polyphosphates. NPP1 has been identified in
proximal and distal tubules of the mouse, while NPP3 is expressed in the rat glomerulus and pars recta, but not in more distal
segments. Ecto-5′-nucleotidase, which catalyses the conversion of AMP to adenosine, is found in apical membranes of rat proximal
convoluted tubule and intercalated cells of the distal nephron, as well as in the peritubular space. Finally, an alkaline
phosphatase, which can theoretically catalyse the entire hydrolysis chain from nucleoside triphosphate to nucleoside, has
been identified in apical membranes of rat proximal tubules; however, this enzyme exhibits relatively high
K
m values for adenine nucleotides. Although information on renal ectonucleotidases is still incomplete, the enzymes’ varied
distribution in the vasculature and along the nephron suggests that they can profoundly influence purinoceptor activity through
the hydrolysis, and generation, of agonists of the various purinoceptor subtypes. This review provides an update on renal
ectonucleotidases and speculates on the functional significance of these enzymes in terms of glomerular and tubular physiology
and pathophysiology.
Keywords Renal tubule - Ectonucleotidases - Ectonucleoside triphosphate diphosphohydrolases - Ectonucleotide pyrophosphatase/phosphodiesterases - Ecto-5′-nucleotidase - Alkaline phosphatases