Abstract
Objective: The aim of this study was to determine if arachidonic acid (AA)-induced skeletal muscle arteriolar dilation is altered with hypercholesterolemia in ApoE and low-density lipoprotein receptor (LDLR) gene deletion mice fed a normal diet. This study also determined contributors to altered AA-induced dilation between dyslipidemic mice and controls, C57/Bl/6J (C57).
Methods: Gracilis muscle arterioles were isolated, with mechanical responses assessed following a challenge with AA under control conditions and after elements of AA metabolism pathways were inhibited. Conduit arteries from each strain were used to assess AA-induced production of PGI2 and TxA2.
Results: Arterioles from ApoE and LDLR exhibited a blunted dilation to AA versus C57. While responses were cyclo-oxygenase-dependent in all strains, inhibition of thromboxane synthase or blockade of PGH2/TxA2 receptors improved dilation in ApoE and LDLR only. AA-induced generation of PGI2 was comparable across strains, although TxA2 generation was increased in ApoE and LDLR. Arteriolar reactivity to PGI2 and TxA2 was comparable across strains. Treatment with TEMPOL improved dilation and reduced TxA2 production with AA in ApoE and LDLR.
Conclusions: These results suggest that AA-induced arteriolar dilation is constrained in ApoE and LDLR via an increased production of TxA2. While partially due to elevated oxidant stress, additional mechanisms contribute that are independent of acute alterations in oxidant tone.
Acknowledgements
The authors gratefully acknowledge the support provided through the Translational Research Core in the Center for Interdisciplinary Research in Cardiovascular Sciences at the West Virginia University Health Sciences Center (Morgantown, Virginia, USA) in the performance of this study.
This study was supported by the American Heart Association (EIA 0740129N) and the National Institutes of Health (R01 DK64668).