ASN's Mission

To create a world without kidney diseases, the ASN Alliance for Kidney Health elevates care by educating and informing, driving breakthroughs and innovation, and advocating for policies that create transformative changes in kidney medicine throughout the world.

learn more

Contact ASN

1401 H St, NW, Ste 900, Washington, DC 20005


The Latest on Twitter

Kidney Week

Abstract: FR-PO319

Deletion of SPAK (Stk39) Reduces Hypertension, NKCC2 Phosphorylation and NKCC2 Activity in Dahl Salt-Sensitive Rats

Session Information

Category: Hypertension and CVD

  • 1403 Hypertension and CVD: Mechanisms


  • Garcia-Pedraza, Jose A., Henry Ford Hospital, Detroit, United States
  • Liao, Tang-Dong, Henry Ford Hospital, Detroit, Michigan, United States
  • Ortiz, Pablo A., Henry Ford Hospital, Detroit, Michigan, United States

The Na/K/2Cl cotransporter NKCC2 mediates the NaCl reabsorption in the thick ascending limb (TAL), playing a crucial role in blood pressure regulation. NKCC2 can be phosphorylated by the SPAK kinase (Stk39) at Thr96,101 and this is thought to activate NKCC2. We found that NKCC2 phosphorylation was 5-fold higher in TALs from Dahl salt-sensitive (DSS) rats. However, the role of SPAK in NKCC2 function and salt-sensitive hypertension remain unclear. We hypothesized that SPAK is involved in salt-sensitive hypertension in part by increasing NKCC2 phosphorylation and activity.


To test this, we generated SPAK knockout (KO) rats in a DSS genetic background via Crispr/Cas9 targeting. We used telemetry to measure systolic blood pressure (SBP) on normal (0.22% Na) or high salt diet (4% Na).


At baseline, SPAK-KO had lower SBP than wild-type DSS (WT) rats (SPAK-KO: 139±1, WT: 153±2 mmHg; p<0.05). After 4 weeks on high salt, SBP rose reaching 162±3 in SPAK-KO and 183±3 mmHg in WT rats (p<0.05). The increase in SBP after feeding a high salt diet was lower in SPAK-KO than WT rats at 7 days (10±1 vs 15±1 mmHg, p<0.05), 14 days (14±2 vs 19±2 mmHg, p<0.05), and 28 days (22±3 vs 30±2 mmHg, p<0.05). We measured total and phospho-NKCC2 in isolated TALs. On normal salt diet, phospho-NKCC2 (Thr96,101) over total NKCC2 was 61±25% lower in SPAK-KO (p<0.05), whereas total NKCC2 was not different. After 4 weeks on high salt, phospho-NKCC2 was 62±13% lower in SPAK-KO (p<0.05) whereas total NKCC2 was not different. SPAK-KO rats had a decreased bumetanide-induced natriuresis while on a normal salt diet (UNa WT: 1271±55; UNa SPAK-KO: 843±80 µmol/12h; p<0.05). Lymphocyte infiltration (CD3+) into the kidney after 4 weeks on high salt diet was not different between strains, whereas CD68+ macrophages were lower in SPAK-KO (WT: 266±35, SPAK-KO: 150±6 CD68+/mm2, p<0.05).


We conclude that SPAK-KO DSS rats exhibit lower SBP at baseline and reduced salt-sensitivity in part caused by lower NKCC2 phosphorylation and activity. In addition, decreased macrophage infiltration in SPAK KO rats supports a potential role for SPAK in renal inflammation during salt-sensitive hypertension.


  • NIDDK Support