Sexual dimorphism in rabbit aortic endothelial function under acute hyperglycemic conditions and gender-specific responses to acute 17β-estradiol

Abstract

Epidemiological data suggest that hyperglycemia abrogates the gender-based cardiovascular protection possibly associated with estrogens. This study was designed to investigate 1) whether rabbit aortic rings show gender differences in the development of abnormal endothelium-dependent vasodilation (EDV) under acute hyperglycemic conditions, 2) the potential role of PKC isoforms and superoxide (O2−) in acute hyperglycemia-induced vascular dysfunction, and 3) the effect of acute estrogen administration on hyperglycemia-induced endothelial dysfunction in male and female rabbits. EDV to ACh was determined before and after 3 h of treatment with high glucose (HG) in phenylephrine-precontracted aortic rings from male and female New Zealand White rabbits. Similar experiments were conducted in the presence of inhibitors of PKC-α, PKC-β, and PKC-δ or an O2− scavenger. The effect of acute estrogen administration was evaluated in the presence and absence of HG. Finally, mRNA expression of PKC isoforms was measured by real-time PCR. We found that 1) 3 h of incubation with HG impairs EDV to a greater extent in female than male aorta, 2) inhibition of PKC-β or O2− prevents HG-induced impairment of EDV in female aorta, 3) acute 17β-estradiol aggravates HG-induced endothelial dysfunction in female, but not male, aorta, and 4) PKC-α and PKC-β expression are significantly higher in female than male aorta. This study reveals the predisposition of female rabbit aorta to vascular injury under hyperglycemic conditions, possibly via activation of PKC-β and O2− production. Furthermore, it suggests that, under hyperglycemic conditions, acute estrogen treatment is detrimental to endothelial function in female rabbits.