We tested the hypothesis that previously demonstrated gender differences in ACh-induced vascular relaxation could involve diverse Na⁺-K⁺-ATPase functions. We determined Na⁺-K⁺-ATPase by measuring arterial ouabain-sensitive⁸⁶Rb uptake in response to ACh. We found a significant increase of Na⁺pump activity only in aortic rings from female rats (control 206 ± 11 vs. 367 ± 29 nmol⁸⁶Rb/K·min^–1·g wt tissue^–1; P < 0.01). Ovariectomy eliminated sex differences in Na⁺-K⁺-ATPase function, and chronic in vivo hormone replacement with 17β-estradiol restored the ACh effect on Na⁺-K⁺-ATPase. Because ACh acts by enhancing production of NO, we examined whether the NO donor sodium nitroprusside (SNP) mimics the action of ACh on Na⁺-K⁺-ATPase activity. SNP increased ouabain-sensitive⁸⁶Rb uptake in denuded female arteries (control 123 ± 7 vs. 197 ± 12 nmol⁸⁶Rb/K·min^–1·g wt tissue^–1; P < 0.05). Methylene blue (an inhibitor of guanylate cyclase) and KT-5823 (a cGMP-dependent kinase inhibitor) blocked the stimulatory action of SNP. Exposure of female thoracic aorta to the Na⁺/K⁺pump inhibitor ouabain significantly decreased SNP-induced and ACh-mediated relaxation of aortic rings. At the molecular level, Western blot analysis of arterial tissue revealed significant gender differences in the relative abundance of catalytic isoforms of Na⁺-K⁺-ATPase. Female-derived aortas exhibited a greater proportion of α₂-isoform (44%) compared with male-derived aortas. Furthermore, estradiol upregulated the expression of α₂mRNA in male arterial explants. Our results demonstrate that enhancement of ACh-induced relaxation observed in female rats may be in part explained by 1) NO-dependent increased Na⁺-K⁺-ATPase activity in female vascular tissue and 2) greater abundance of Na⁺-K⁺-ATPase α₂-isoform in females.

Calcium signaling in vascular endothelial cells (ECs) and smooth muscle cells (VSMCs) is essential for the regulation of vascular tone. However, the changes to intracellular Ca²⁺ concentrations are often influenced by sex differences. Furthermore, a large body of evidence shows that sex hormone imbalance leads to dysregulation of Ca²⁺ signaling and this is a key factor in the pathogenesis of cardiovascular diseases. In this review, the effects of estrogens and androgens on vascular calcium-handling proteins are discussed, with emphasis on the associated genomic or nongenomic molecular mechanisms. The experimental models from which data were collected were also considered. The review highlights 1) in female ECs, transient receptor potential vanilloid 4 (TRPV4) and mitochondrial Ca²⁺ uniporter (MCU) enhance Ca²⁺-dependent nitric oxide (NO) generation. In males, only transient receptor potential canonical 3 (TRPC3) plays a fundamental role in this effect. 2) Female VSMCs have lower cytosolic Ca²⁺ levels than males due to differences in the activity and expression of stromal interaction molecule 1 (STIM1), calcium release-activated calcium modulator 1 (Orai1), calcium voltage-gated channel subunit-α_1C (Ca_V1.2), Na⁺-K⁺-2Cl⁻ symporter (NKCC1), and the Na⁺/K⁺-ATPase. 3) When compared with androgens, the influence of estrogens on Ca²⁺ homeostasis, vascular tone, and incidence of vascular disease is better documented. 4) Many studies use supraphysiological concentrations of sex hormones, which may limit the physiological relevance of outcomes. 5) Sex-dependent differences in Ca²⁺ signaling mean both sexes ought to be included in experimental design.

The aim of this work is to determine whether consuming tap water containing arsenic (20 μg/L) alters oxidative stress levels in female rats and changes vascular response. Whereas nitric oxide produces complete relaxation, arsenic (7 months of exposure) impairs the acetylcholine-induced endothelial relaxation in the rat aorta compared with control rats. Arsenic exposure results in a marked elevation in reactive oxygen species in blood, and δ-aminolevulinic acid dehydratase activity, which is a sensitive biomarker for arsenic toxicity and oxidative stress, is significantly decreased in erythrocytes from 7-month-old rats. Diastolic blood pressure increases significantly in 7-month-old arsenic-treated versus control rats. The percentage of change in peripheral resistance increases. The results indicate that chronic environmental exposure to low levels of arsenic alters the release of vasoactive substances, causes changes in oxidative stress, and increases blood pressure in female rats.