Effects of High Glucose and Major Metabolic Substrates on Alpha-adrenergic Contractions in Rat Mesenteric and Deep Femoral Arteries

Abstract

Hyperglycemia causes vascular damage and increased risk of cardiovascular diseases. It has been demonstrated that chronic exposure to high glucose impaired endothelial functions. However, specific effects of short-term exposure to high glucose on vascular reactivity are controversial. Moreover, the combined effects of other metabolic substrates such as free fatty acids (FFA) on vascular reactivity remain poorly understood. Here we investigate the effects of short-term exposure to high glucose with or without major metabolic substrates including FFAs termed “nutrition with fatty acid” (NF) solution, on mesenteric (MA) and deep femoral arteries (DFA) of rats. Arterial ring segments were mounted in a double-wire myograph. Contraction in response to phenylephrine (PhE) was determined in control (5 mM) and high glucose (23 mM, HG) environments over a 30 min period. Our results showed that PhE-induced vasocontraction was enhanced by pre-incubation of HG solution in both arteries. A combined incubation with HG and palmitic acid (100 mM) induced similar sensitization of PhE-contractions in both arteries. In contrast, high K+-induced contractions were not affected by HG. Interestingly, pre-incubation with NF solution decreased PhE-induced contraction in DFA but increased the contraction in MA. In NF solution, the HG-induced facilitation of PhE-contraction was not observed in MA. Furthermore, the PhE-induced contraction of DFA was attenuated by HG in NF solution. Our results demonstrate that the sensitization of PhE-induced arterial contraction by HG is differentially affected by other metabolic substrates. The conversation of skeletal arterial contractility by HG in NF solution requires careful interpretation of the previous in vitro studies where only glucose is included in physiological salt solutions. Further studies are required to elucidate the mechanism underlying the inconsistent effect of NF solution on MA and DFA.