Fig. 2.

Effect of luminal (L) H89 (10 μM) on basal and flow-stimulated net cation transport in isolated perfused rabbit CCDs. A: J_Na increased in untreated control (C) tubules as the luminal flow rate was increased from ∼1 to 5 nl·min⁻¹·mm⁻¹. H89 added to the luminal solution had no effect on flow-stimulated J_Na. J_Na in 2 tubules perfused with H89 and luminal IBX (10.5 and 17.8 pmol·min⁻¹·mm⁻¹) was similar to that measured in control CCDs and those perfused with H89 alone at a flow rate of ∼1 nl·min⁻¹·mm⁻¹. B: J_K increased ∼3-fold in response to a 5-fold increase in luminal flow rate in control CCDs. Addition of H89 to the luminal solution increased J_K in CCDs perfused at a flow rate of 1 nl·min⁻¹·mm⁻¹; a subsequent increase in flow rate augmented J_K only slightly. J_K in 2 tubules perfused with H89 and luminal IBX (−8.5 and −9.7 pmol·min⁻¹·mm⁻¹) was similar to that measured in control CCDs perfused at a flow rate of ∼1 nl·min⁻¹·mm⁻¹. Values are means ± SE. For each protocol, n is indicated in results. *P < 0.05 compared with J_x at 1 nl·min⁻¹·mm⁻¹ in same tubules. #P < 0.05 compared with J_x in control tubules studied at same flow rate.