Table 3.
Ectonucleotidases in the renal epithelium
| Collecting Duct |
|||||||
|---|---|---|---|---|---|---|---|
| Km, µM (593) | Proximal Tubule | Loop of Henle | CCD/OMCD | IMCD | Interstitial Cells | Peritubular Capillaries | |
| NTPDase1 (CD39) | ATP ~0–200 | tAL (269) | Low IC,PC (530); terminal part (269) | Cortical (269, 304, 530) | |||
| NTPDase2 (CD39L1) | ATP ~70 | TAL (A, B) (530) | Low IC,PC (530) | ||||
| NTPDase3 | ATP ~75 | TAL (A) (530) | IC (530) | Low PC (530) | |||
| NTPDase8 | ATP 81–226 | ||||||
| NPP1 (PC-1) | ATP ~50–500; ApnA ~1–20 | ||||||
| NPP2 | UDP-glucose ~100 | ||||||
| NPP3 | ~200 | PST (A) (530) | |||||
| AP | Low ATP ~40; high ATP ~1,000 | (A) (30) | |||||
| Ecto-5′ NT (CD73) | AMP 1–50 | Early PCT > late PCT > PST (A) (118, 161, 530) | IC (A) (118, 161, 530) | IC (A) (118, 161, 530) | css fibroblasts (161, 295) | ||
AP, alkaline phosphatase; (A), apical; (B), basolateral; CCD, cortical collecting duct; CNT, connecting tubule; css fibroblasts, cortical stellate-shaped fibroblasts; IC, intercalated cells; IMCD, inner medullary collecting duct; Km, the concentration of substrate that permits the enzyme to achieve half-maximal reaction velocity; low, low expression; OMCD, outer medullary collecting duct; PC, principal cell; PCT, proximal convoluted tubule; PST, proximal straight tubule; tAL, thin ascending limb; TAL; thick ascending limb. Studies were performed in rats (30, 118, 161, 269, 295, 530), mice (269), or pigs (304). All studies used immunohistochemistry except Ref. 30, which used alkaline phosphatase activity. Reference numbers are in parentheses. [Adapted from Vallon (523).]