Fig. 3.

A: relationship between urinary ATP excretion and urinary flow rate under different maneuvers. Urinary ATP was reduced by acute vasopressin V₂ receptor inhibition (V₂-I) but increased by acute WL. Increasing urinary flow rate alone is not a good predictor of urinary ATP excretion. For further details, see text. B: a proposed positive relationship between the cell volume, manipulated by different maneuvers in WT and P2Y₂^−/− mice and urinary ATP excretion. We propose that feedback regulation of cell volume via cell volume-regulated ATP release is absent/reduced in P2Y₂^−/− mice resulting in greater ATP release. The influence is minimized by reducing water uptake by V₂-I and maximized by water loading-induced cell swelling. All data are from Ref. 59.