Abstract: SA-PO1050

Probenecid Downregulates Pendrin and Enhances Hydrochlorothiazide–Induced Diuresis

Session Information

  • Na+, K+, Cl-
    November 04, 2017 | Location: Hall H, Morial Convention Center
    Abstract Time: 10:00 AM - 10:00 AM

Category: Fluid, Electrolytes, and Acid-Base

  • 703 Na+, K+, Cl- Basic

Authors

  • Barone, Sharon L., University of Cincinnati, Cincinnati, Ohio, United States
  • Xu, Jie, University of Cincinnati, Cincinnati, Ohio, United States
  • Zahedi, Kamyar A., University of Cincinnati, Cincinnati, Ohio, United States
  • Brooks, Marybeth, University of Cincinnati, Cincinnati, Ohio, United States
  • Soleimani, Manoocher, University of Cincinnati, Cincinnati, Ohio, United States
Background

The inactivation or inhibition of NCC or pendrin does not cause any overt salt wasting under baseline conditions. However, double deletion or inactivation of NCC and pendrin causes severe salt wasting in rodents, indicating an important role for pendrin in compensatory salt absorption in the setting of NCC inhibition.
Probenecid is a uricosuric agent that inhibits the organic anion transporters (OAT) in the proximal tubule and is used in the treatment of hyperuricemia and gout. In addition, probenecid inhibits the ATP transporter Pannexin 1 in the proximal tubule (PT) and the collecting duct, downregulates pendrin in mammary gland cells and possesses a positive ionotropic effect in the heart.
We hypothesized that pretreatment with probenecid will downregulate pendrin, and consequently enhances hydrochlorothiazide (HCTZ) diuresis.

Methods

Male Sprague Dawley rats were treated with probenecid i.p. at 250 or 100 mg/kg/day for 6 days and then received HCTZ daily for 4 days while being maintained on probenecid. Balance studies were performed and expression levels of pendrin and AQP-2 in the kidney were estimated using double immunofluorescence labeling.

Results

Urine output increased from 9.8 at baseline to 15.9 ml/24 hrs after 10 days of Probenecid at 250 mg/kg (p<0.02, n=5). Treatment with HCTZ alone for 4 days caused a mild diuresis, with urine output increasing to 13.8 ml/24 hrs (p>0.05, vs. baseline, n=5). However, rats pretreated with Probenecid for 6 days exhibited a profound diuresis when HCTZ was added for 4 additional days, with urine output increasing to 42.9 ml/day, a more than 300% increase vs. rats treated with either Probenecid or HCTZ (p<0.003 vs. both groups, n = 5). In the absence of pretreatment with Probenecid, the diuresis caused by concurrent Probencid plus HCTZ treatment was similar to HCTZ alone (p>0.05). Immunofluorescent labeling and/or Western hybridization studies demonstrated a significant reduction in the expression of pendrin and AQP2 in the kidney cortical collecting duct/cortex of probenecid treated rats.

Conclusion

Probenecid pretreatment downregulates pendrin and AQP2 and robustly enhances diuresis by HCTZ-mediated NCC inhibition in the distal nephron. We propose that Probenecid followed by HCTZ is a strong diuretic regimen for fluid overloaded states and also prevents the hyperuricemia that is caused by HCTZ.

Funding

  • Veterans Affairs Support