The pathogenesis of hypertension is distinct between men and women. Endothelin-1 (ET-1) is a potential contributor to sex differences in the pathophysiology of hypertension. ET-1 participates in blood pressure regulation through activation of endothelin A (ETA) and endothelin B (ETB) receptors including those in the vasculature. Previous studies demonstrated that sex and sex hormones evoke discrepancies in ET-1-mediated control of vascular tone in different vascular beds. However, little is known about sex- and sex hormone-related differences in ET-1-dependent renal microvascular reactivity. Accordingly, we hypothesized that loss of sex hormones impairs afferent arteriole reactivity to ET-1. Male and female Sprague Dawley rats were subjected to gonadectomy or sham surgery (n = 6/group). After 3 weeks, kidneys from those rats were prepared for assessment of renal microvascular responses to ET-1 (ETA and ETB agonist, 10−12 to 10−8 M) and sarafotoxin 6c (S6c, ETB agonist, 10−12 to 10−8 M) using the blood-perfused juxtamedullary nephron preparation. Control afferent arteriole diameters at 100 mmHg were similar between sham male and female rats averaging 14.6 ± 0.3 and 15.3 ± 0.3 μm, respectively. Gonadectomy had no significant effect on control arteriole diameter. In sham males, ET-1 produced significant concentration-dependent decreases in afferent arteriole diameter, with 10−8 M ET-1 decreasing diameter by 84 ± 1%. ET-1 induced similar concentration-dependent vasoconstrictor responses in sham female rats, with 10−8 M ET-1 decreasing the diameter by 82 ± 1%. The afferent arteriolar vasoconstrictor responses to ET-1 were unchanged by ovariectomy or orchiectomy. Selective ETB receptor activation by S6c induced a concentration-dependent decline in afferent arteriole diameter, with 10−8 M S6c decreasing diameter by 77 ± 3 and 76 ± 3% in sham male and female rats, respectively. Notably, ovariectomy augmented the vasoconstrictor response to S6c (10−12 to 10−9 M), whereas orchiectomy had no significant impact on the responsiveness to ETB receptor activation. These data demonstrate that sex does not significantly influence afferent arteriole reactivity to ET receptor activation. Gonadectomy potentiated the responsiveness of the afferent arteriole to ETB-induced vasoconstriction in females, but not males, suggesting that female sex hormones influence ETB-mediated vasoconstriction in the renal microcirculation.

Raloxifene hydrochloride (RLX) is a selective estrogen-receptor modulator for treatment of osteoporosis and prevention of breast and endometrial cancer. By virtue of extensive presystemic clearance, RLX bioavailability is only 2%. The current study aimed to tailor and characterize RLX-loaded self-nanoemulsifying drug-delivery systems (SNEDDS) using bioactive excipients affecting drug metabolism. The potential of oral nanocarriers to enhance RLX delivery to endocrine target organs was assessed in fasted and fed female Wistar rats using high-performance liquid chromatography. RLX was loaded in the dissolved and dispersed status in the alkalinized (A-SNEDDS) and nonalkalinized (NA-SNEDDS) systems, respectively. Optimization and assessment relied on solubility studies, emulsification efficiency, phase diagrams, dilution robustness, cloud point, particle size, zeta potential (ZP), polydispersity index (PDI), and transmission electron microscopy. In vitro release was assessed using dialysis bag versus dissolution cup methods. NA-SNEDDS were developed with suitable globule size (38.49 ± 4.30 nm), ZP (31.70 ± 3.58 mV), PDI (0.31 ± 0.02), and cloud point (85°C). A-SNEDDS exhibited good globule size (35 ± 2.80 nm), adequate PDI (0.28 ± 0.06), and lower ZP magnitude (-21.20 ± 3.46 mV). Transmission electron microscopy revealed spherical globules and contended data of size analysis. Release studies demonstrated a nonsignificant enhancement of RLX release from NA-SNEDDS compared to drug suspension with the lowest release shown by A-SNEDDS. A conflicting result was elucidated from in vivo trial. A significant enhancement in RLX uptake by endocrine organs was observed after nanocarrier administration compared to RLX suspension. In vivo studies reflected a poor in vitro/in vivo correlation, recommended nanocarrier administration before meals, and did not reveal any advantage for drug loading in the solubilized form (A-SNEDDS). To conclude, NA-SNEDDS possessed superior in vitro characteristics to A-SNEDDS, with equal in vivo potential. NA-SNEDDS elaborated in this work could successfully double RLX delivery to endocrine target organs, with promising consequences of lower dose and side effects of the drug.

Background: Premenopausal women are less likely to develop hypertension and salt‐related complications than are men, yet the impact of sex on mechanisms regulating Na ⁺ homeostasis during dietary salt challenges is poorly defined. Here, we determined whether female rats have a more efficient capacity to acclimate to increased dietary salt intake challenge. Methods and Results: Age‐matched male and female Sprague Dawley rats maintained on a normal‐salt (NS) diet (0.49% NaCl) were challenged with a 5‐day high‐salt diet (4.0% NaCl). We assessed serum, urinary, skin, and muscle electrolytes; total body water; and kidney Na ⁺ transporters during the NS and high‐salt diet phases. During the 5‐day high‐salt challenge, natriuresis increased more rapidly in females, whereas serum Na ⁺ and body water concentration increased only in males. To determine if females are primed to handle changes in dietary salt, we asked the question whether the renal endothelin‐1 natriuretic system is more active in female rats, compared with males. During the NS diet, female rats had a higher urinary endothelin‐1 excretion rate than males. Moreover, Ingenuity Pathway Analysis of RNA sequencing data identified the enrichment of endothelin signaling pathway transcripts in the inner medulla of kidneys from NS‐fed female rats compared with male counterparts. Notably, in human subjects who consumed an Na ⁺ ‐controlled diet (3314–3668 mg/day) for 3 days, women had a higher urinary endothelin‐1 excretion rate than men, consistent with our findings in NS‐fed rats. Conclusions: These results suggest that female sex confers a greater ability to maintain Na ⁺ homeostasis during acclimation to dietary Na ⁺ challenges and indicate that the intrarenal endothelin‐1 natriuretic pathway is enhanced in women.

Background: The novel estrogen receptor, G‐protein–coupled estrogen receptor ( GPER ), is responsible for rapid estrogen signaling. GPER activation elicits cardiovascular and nephroprotective effects against salt‐induced complications, yet there is no direct evidence for GPER control of renal Na ⁺ handling. We hypothesized that GPER activation in the renal medulla facilitates Na ⁺ excretion. Methods and Results: Herein, we show that infusion of the GPER agonist, G1, to the renal medulla increased Na ⁺ excretion in female Sprague Dawley rats, but not male rats. We found that GPER mRNA expression and protein abundance were markedly higher in outer medullary tissues from females relative to males. Blockade of GPER in the renal medulla attenuated Na ⁺ excretion in females. Given that medullary endothelin 1 is a well‐established natriuretic factor that is regulated by sex and sex steroids, we hypothesized that GPER activation promotes natriuresis via an endothelin 1–dependent pathway. To test this mechanism, we determined the effect of medullary infusion of G1 after blockade of endothelin receptors. Dual endothelin receptor subtype A and endothelin receptor subtype B antagonism attenuated G1‐induced natriuresis in females. Unlike males, female mice with genetic deletion of GPER had reduced endothelin 1, endothelin receptor subtype A, and endothelin receptor subtype B mRNA expression compared with wild‐type controls. More important, we found that systemic GPER activation ameliorates the increase in mean arterial pressure induced by ovariectomy. Conclusions: Our data uncover a novel role for renal medullary GPER in promoting Na ⁺ excretion via an endothelin 1–dependent pathway in female rats, but not in males. These results highlight GPER as a potential therapeutic target for salt‐sensitive hypertension in postmenopausal women.

Sex differences in redox signaling in the kidney present new challenges and opportunities for understanding the physiology and pathophysiology of the kidney. This review will focus on reactive oxygen species, immune-related signaling pathways and endothelin-1 as potential mediators of sex-differences in redox homeostasis in the kidney. Additionally, this review will highlight male-female differences in redox signaling in several major cardiovascular and renal disorders namely acute kidney injury, diabetic nephropathy, kidney stone disease and salt-sensitive hypertension. Furthermore, we will discuss the contribution of redox signaling in the pathogenesis of postmenopausal hypertension and preeclampsia.