Flow-activated Na + and HCO 3 transport in kidney proximal tubules (PTs) underlies relatively constant fractional reabsorption during changes in glomerular filtration rate (GFR), or glomerulotubular balance (GTB). In view of hypothesized connections of epithelial cilia to flow-sensing, we examined flow-activated transport in three polycystic kidney disease-related mouse models based on inducible conditional knockout (KO) of Pkd1, Pkd2, and Kif3a. PTs.were harvested from mice after gene inactivation but prior to cyst formation, and flow-mediated PTs transport were measured. We confirm that higher flow increases both Na + and HCO 3 absorption in control and observe that this flow effect is preserved in PTs of Pkd1 -/and Kif3a -/mice. However, flow-activation is absent in Pkd2 +/and Pkd2 -/proximal tubules. In heterozygous (Pkd2 +/-) mice, a dopamine receptor (DA1) antagonist (SCH23390) restored transport flow sensitivity. When given chronically, this same antagonist reduced renal cyst formation in Pkd2 -/as evidenced by reduced kidney weight, BUN and the cystic index, when compared to untreated mice. In contrast, SCH23390 did not prevent cyst formation in Pkd1 -/mice. These results indicate that Pkd2 is necessary for normal GTB, and that restoration of flowactivated transport by DA1 antagonist can slow renal cyst formation in Pkd2 -/mice.