Activation of G Protein‐coupled Estrogen Receptor Promotes Endothelin‐dependent Natriuresis in Female Rats

Abstract

The novel estrogen receptor, G protein‐coupled estrogen receptor (GPER), is a membrane‐bound receptor linked to acute signaling pathways. GPER activation elicits cardiovascular and nephroprotective effects against salt‐induced complications. However, its specific role in renal sodium handling is not yet defined. We hypothesized that activation of GPER in the renal medulla facilitates sodium excretion. Isosmotic saline was infused into the renal medullary interstitium (500 μl/h) of anesthetized male and female Sprague‐Dawley rats for an 80 min equilibration period and 20 min baseline urine collection period. Then, G1 (GPER agonist, 50 pmol/kg/min) or vehicle was infused into the renal medulla for an additional 20 min period. Compared with vehicle, G1 significantly increased urinary sodium excretion in females (from 0.6 ± 0.1 to 1.0 ± 0.1 μmol/min n=9, p<0.05). G1 did not change blood pressure or urinary potassium excretion in comparison with vehicle control (106 ± 3 vs. 105 ± 4 mmHg, 0.5 ± 0.1 vs. 0.4 ± 0.1 μmol/min, n=9). Medullary blood flow remained unchanged during these experiments. In males, G1 did not change urinary sodium excretion (from 0.6 ± 0.1 to 0.7 ± 0.1 μmol/min, n=9). No sex‐differences in medullary GPER mRNA expression was observed, suggesting that sex‐differences in G1 effects on sodium excretion could be related to GPER downstream signaling cascade. Given that endothelin‐1 (ET‐1) is a well‐established natriuretic factor that is regulated by sex and sex steroids, we hypothesized that GPER activation promotes natriuresis via an ET‐1‐dependent pathway. To test this idea, we studied the effect of medullary infusion of G1 after dual blockade of ETA and ETB receptors achieved by i.v. bolus injection of ABT‐627 (5 mg/kg) and A‐192621 (10 mg/kg), respectively. We found that the natriuretic response to medullary GPER activation in females was inhibited by dual blockade of ET‐1 receptors (from 0.5 ± 0.2 to 0.5 ± 0.2 μmol/min n=5). These data uncover a novel role for renal medullary GPER in promoting sodium excretion via an ET‐1‐dependent pathway in females, but not in males.Support or Funding InformationFunded by AHA 15POST25090329 to EYG and P01 HL136267 to DMP and JSPThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.