Kidney Week

Abstract: FR-OR24

PIEZO1 Channels Are Necessary for BK Channel-Mediated Flow-Induced K+ Secretion (FIKS) in the Cortical Collecting Duct (CCD)

Session Information

• Fluid, Electrolyte, and Acid-Base Disorders: Basic Research
  November 03, 2023 | Location: Room 111, Pennsylvania Convention Center
  Abstract Time: 04:57 PM - 05:06 PM

Category: Fluid, Electrolytes, and Acid-Base Disorders

• 1101 Fluid, Electrolyte, and Acid-Base Disorders: Basic

Authors

• Carrisoza-Gaytan, Rolando, Icahn School of Medicine at Mount Sinai Department of Pediatrics, New York, New York, United States

Rolando Carrisoza-Gaytan, PhD

• Mutchler, Stephanie, University of Pittsburgh Department of Medicine, Pittsburgh, Pennsylvania, United States

Stephanie Mutchler,

• Dalghi, Marianela G., University of Pittsburgh Department of Medicine, Pittsburgh, Pennsylvania, United States

Marianela G. Dalghi,

• Carattino, Francisco, Icahn School of Medicine at Mount Sinai Department of Pediatrics, New York, New York, United States

Francisco Carattino,

• Apodaca, Gerard, University of Pittsburgh Department of Medicine, Pittsburgh, Pennsylvania, United States

Gerard Apodaca,

• Kleyman, Thomas R., University of Pittsburgh Department of Medicine, Pittsburgh, Pennsylvania, United States

Thomas R. Kleyman,

• Satlin, Lisa M., Icahn School of Medicine at Mount Sinai Department of Pediatrics, New York, New York, United States

Lisa M. Satlin,

Background

BK channel-mediated FIKS in intercalated cells (IC) of the CCD requires an elevation in intracellular calcium concentration [Ca²⁺]_i triggered by hydrodynamic forces associated with an increase in tubular fluid flow rate (TFFR). This increase in [Ca²⁺]_i is proposed to be due to influx of extracellular Ca²⁺ through apical and basolateral mechanosensitive Ca²⁺ channels and release of Ca²⁺ from internal stores. We previously identified functional expression of the mechanosensitive Ca²⁺ channel PIEZO1 at the basolateral membranes of CCD principal (PC) and ICs (ASN Kidney Week, 2021). We hypothesize that PIEZO1 contributes to the flow-induced increase in [Ca²⁺]_i necessary for BK channel-mediated FIKS.

Methods

To test this hypothesis, control and conditional IC-cell Piezo1 KO mice were fed a high K⁺ diet (HK, 5% K⁺) for 10 d. Isolated CCDs were microperfused in vitro to measure flow-induced increases in [Ca²⁺]_i and net transepithelial transport (J_X) of Na⁺ and K⁺ at slow and fast tubular fluid flow rates (0.9 and 5.5 nl/min^.mm).

Results

Both PCs and ICs from control mice exhibited typical biphasic increases in [Ca²⁺]_i in response to an acute increase in TFFR. However, flow-induced [Ca²⁺]_i transients were significantly dampened in ICs from conditional IC-cell Piezo1 KO mice (p≤0.001, n=4/group). Similar rates (in pmol/min.mm) of flow-stimulated J_Na were observed in CCDs from control (49.9±5.5) and KO (51.2±5.2, p=0.7; n=6, including 3 male and 3 female/group) mice with no significant differences between sex. FIKS, present in control CCDs (5.3±1.2), was absent in tubules from conditional KO mice (1.0±1.2; p<0.005). IC-cell Piezo1 KO male mice exhibited higher blood [K⁺] vs controls, 30 and 60 mins after gavage administration of 5% KCl solution (7.8±0.91 and 6.4±0.89 vs 6.5±0.35 and 5.1±0.17 mmol/L, n=6/group; p=0.01 and 0.02 respectively).

Conclusion

We conclude that mechanoactivated PIEZO1 channels mediate basolateral influx of Ca²⁺ in CCD ICs, and are indispensable for BK channel-mediated FIKS. We further speculate that basolateral PIEZO1 channels are activated by increases in membrane tension associated with an increase in TFFR.

Funding

• NIDDK Support