Endothelin Receptor A and B Co‐operate to Mediate GPER‐induced Natriuresis

Abstract

G protein‐coupled estrogen receptors (GPER) are membrane‐associated receptors that mediate rapid estrogenic signaling. We recently found that activation of GPER in the renal medulla of female rats, but not males, evokes endothelin‐dependent natriuresis. Endothelin‐1 (ET‐1) inhibits tubular reabsorption of Na+ via stimulating ET receptor B (ETB). Evidence points that ET receptor A (ETA) may contribute to natriuresis in female rats only. The current study was designed to identify whether GPER‐induced natriuresis is mediated via activation of renal medullary ETA and/or ETBreceptors in female rats. We determined the effect of stimulating GPER in the renal medulla on urine flow and urinary Na+ excretion in anesthetized female ETB deficient rats (ETB def) and transgenic (TG) controls. We infused saline to the renal medullary interstitium during an equilibration period of 60–80 min at a flow rate of 500 μl/h, followed by vehicle, then the GPER selective agonist, G1 (5 pmol/kg/min). Infusion of G1 to the renal medulla increased urine flow and Na+excretion in TG control animals (from 4.77 ± 1.19 to 7.36 ± 2.41 μl/min and from 0.47 ± 0.09 to 0.91 ± 0.27 μmol/min, respectively, n=7, p<0.05). Similarly, medullary GPER activation evoked a diuretic and natriuretic response in ETB def rats (urine flow: from 4.07 ± 0.47 to 6.52 ± 1.01 μl/min and Na+ excretion: from 0.29 ± 0.06 to 0.64 ± 0.16 μmol/min, respectively, n=8, p<0.05). G1 infusion did not change blood pressure or urinary K+ excretion in ETB def or TG control animals. Mean arterial blood pressure was higher in ETB def rats, compared to TG controls (117 ± 6 vs. 99 ± 3 mmHg, n=7–8, p<0.05). We also determined the physiological response to medullary GPER activation in anesthetized female Sprague Dawley rats after individual blockade of ETA or ETB receptors, achieved by an intravenous bolus injection of ABT‐627 (5mg/kg) or A‐192621 (10 mg/kg), respectively, or vehicle. Neither selective antagonism of ETA nor ETB antagonism impacted the diuretic or natriuretic actions of G1. However, simultaneous blockade of ETA and ETB receptors abolished G1‐evoked diuresis and natriuresis. Blood pressure and urinary K+ excretion remained unchanged during G1 infusion in the presence or absence of ET receptor antagonists. Thus, using pharmacological and genetic approaches, our study reveals that ETA and ETB receptors in the renal medulla work co‐operatively to mediate the diuretic and natriuretic response to GPER activation.Support or Funding InformationFunded by AHA 18CDA34110010 and K99DK119413 to EYG and P01 HL136267 to DMP.