Fig. 4.

Proposed models for the interaction among AVP, purinergic (ATP) and prostanoid (PGE₂) systems in medullary collecting duct principal cell under normal condition (left), and how they are deranged in acquired NDI (right). (−) and (+) signs denote inhibition and stimulation, respectively. X marks indicate blocked pathways. Thicker arrows indicate accentuation of pathways. The letters A, B, C, D and E are keyed to the explanations in the text