Direct inhibition of basolateral K_ir4.1/5.1 and K_ir4.1 channels in the cortical collecting duct by dopamine

Abstract

It is recognized that dopamine promotes natriuresis by inhibiting multiple transporting systems in the proximal tubule. In contrast, less is known about the molecular targets of dopamine actions on water-electrolyte transport in the cortical collecting duct (CCD). Epithelial cells in the CCD are exposed to dopamine, which is synthesized locally or secreted from sympathetic nerve endings. Basolateral K(+) channels in the distal renal tubule are critical for K(+) recycling and controlling basolateral membrane potential to establish the driving force for Na(+) reabsorption. Here, we demonstrate that Kir4.1 and Kir5.1 are highly expressed in the mouse kidney cortex and are localized to the basolateral membrane of the CCD. Using patch-clamp electrophysiology in freshly isolated CCDs, we detected highly abundant 40-pS and scarce 20-pS single channel conductances, most likely representing Kir4.1/5.1 and Kir4.1 channels, respectively. Dopamine reversibly decreased the open probability of both channels, with a relatively greater action on the Kir4.1/5.1 heterodimer. This effect was mediated by D2-like but not D1-like dopamine receptors. PKC blockade abolished the inhibition of basolateral K(+) channels by dopamine. Importantly, dopamine significantly decreased the amplitude of Kir4.1/5.1 and Kir4.1 unitary currents. Consistently, dopamine induced an acute depolarization of basolateral membrane potential, as directly monitored using current-clamp mode in isolated CCDs. Therefore, we demonstrate that dopamine inhibits basolateral Kir4.1/5.1 and Kir4.1 channels in CCD cells via stimulation of D2-like receptors and subsequently PKC. This leads to depolarization of the basolateral membrane and a decreased driving force for Na(+) reabsorption in the distal renal tubule.

IGF-1 and insulin exert opposite actions on ClC-K2 activity in the cortical collecting ducts

“…Previous reports showed that similar concentrations of the antagonists drastically reduced ClC-K2 activity in renal tubule cells (1,28). We focused on IC having values of basolateral membrane voltage of ϳϪ10 mV, in contrast to PC having basolateral membrane voltage of Ϫ70 mV (47). NPPB treatment has no measurable effect on the basolateral membrane voltage (n ϭ 5), whereas replacement of bath NaCl for NaCitrate elicits prominent depolarization, as expected (Fig.…”

“…The procedure for isolation of the CCDs suitable for electrophysiology is a modification from the protocols described previously (23,24,26,47). Mice were killed by CO 2 administration followed by cervical dislocation and the kidneys were removed immediately.…”

Essential role of Kir5.1 channels in renal salt handling and blood pressure control

“…The heteromeric K ir 4.1/K ir 5.1 channel has unique properties, including single-channel conductance that is greater than that of the homomeric K ir 4.1 (13)(14)(15). We and others reported that the K ir 4.1/K ir 5.1 heteromer is the predominant basolateral K + channel in both the DCT and CCD (16)(17)(18)(19). In humans, loss-of-function mutations in the KCNJ10 gene have been shown to cause epilepsy, ataxia, sensorineural deafness and tubulopathy (EAST/SeSAME) syndrome (20)(21)(22).…”

Development and Validation of Fluorescence-Based and Automated Patch Clamp–Based Functional Assays for the Inward Rectifier Potassium Channel Kir4.1

“…Kir4.1/5.1 inhibitors that act directly on the basolateral membrane should circumvent this limitation. Furthermore, Zaika et al (2013) reported recently that dopamine inhibits Na + reabsorption in the cortical collecting duct (CCD) through inhibition of Kir4.1 homomeric and Kir4.1/5.1 heteromeric channels. 17 Conceivably, Kir4.1/5.1…”