Volume 31, Issue S1 p. 703.20-703.20
Physiology
Free Access

Effect of Diuretics and Gender on Kcnj16-mediated Effects in Salt Sensitive Hypertension

Oleg Palygin

Oleg Palygin

Physiology, Medical College of Wisconsin, Milwaukee, WI

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Vladislav Levchenko

Vladislav Levchenko

Physiology, Medical College of Wisconsin, Milwaukee, WI

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Oleh Prudnikov

Oleh Prudnikov

Physiology, Medical College of Wisconsin, Milwaukee, WI

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Christine Nguyen

Christine Nguyen

Physiology, Medical College of Wisconsin, Milwaukee, WI

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Alexander Staruschenko

Alexander Staruschenko

Physiology, Medical College of Wisconsin, Milwaukee, WI

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Abstract

Hypokalemia is a potentially life-threatening imbalance characterized by a serum potassium concentration of less than 3.5mmol/L (severe hypokalemia < 2.5mmol/L) caused by a deficit in total body potassium stores induced by dietary, genetic or iatrogenic factors. Inwardly-rectifying K+ channels Kir4.1 (Kcnj10) and Kir5.1 (Kcnj16) are highly expressed on the basolateral membrane of distal renal tubules and contribute to Na+ reabsorption and K+ secretion through the direct control of trans-epithelial voltage. To define the importance of Kir5.1 in electrolyte balance and potassium homeostasis in the body, we generated a Kcnj16 knockout in Dahl salt-sensitive (SS) rats (SSKcnj16−/−). SSKcnj16−/− rats fed a normal 0.4% NaCl diet (Dyets) had severe hypokalemia (3.8±0.03 vs 2.00±0.06, mmol/L; SS vs SSKcnj16−/− rats correspondingly, p<0.05, N≥9) and reduced blood pressure. Female rats had an even more profound change in blood potassium (3.5±0.04 vs 1.55±0.04 mmol/L; SS vs SSKcnj16−/− rats correspondingly, p<0.05, N≥11). Overall fractional excretion analyses further revealed that SSKcnj16−/− rats had a salt-wasting phenotype with increased FENa+, FEK+, and FEMg2+. When fed a high salt diet (4% NaCl; Dyets) SSKcnj16−/− rats experienced 100% mortality triggered by diuresis-natriuresis and a further drop of blood potassium level below 1.4mmol/L. To reduce mortality and preserve potassium wasting under high salt conditions, we supplemented the drinking water of the SSKcnj16−/− rats with inhibitors of sodium channels and transporters critical for maintenance of electrolyte homeostasis in the Thick Ascending Limb (TAL) (furosemide; 150mg/L), Distal Convoluted Tubule (DCT) (Hydrochlorothiazide (HCTZ) 75mg/L) and Cortical Collecting Duct (CCD) (benzamil 15mg/L) (N≥6 for males and females in each treatment group). Epithelial sodium channel (ENaC) inhibitor benzamil, but not other diuretics, rescued SSKcnj16−/− rats from mortality on the high salt diet, but removal of benzamil from the drinking water after two weeks of high salt treatment still resulted in mortality. Interestingly, treatment with HCTZ delayed mortality only in males and had no effect in females, emphasizing the role of the DCT segment specifically in male SSKcnj16−/− rats. Together, our data with diuretics targeting NKCC, NCC and ENaC revealed that only benzamil treatment rescued SSKcnj16−/− rats when challenged with a high salt diet, and furthermore we have demonstrated gender differences important in regulation of Kcnj16-mediated effects in the kidney.

Support or Funding Information

Medical College of Wisconsin Neuroscience Research Center/Advancing a Healthier Wisconsin pilot grant #9520217 (to OPa) and National Institutes of Health grants HL108880, HL122662 (to AS)