Date of Award

5-2007

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Food Science and Human Nutrition

Advisor

Dorothy Klimis-Zacas

Second Committee Member

Rodney Bushway

Third Committee Member

Linda Kling

Abstract

We examined the effect(s) of wild blueberries on the major vasodilation pathways of Sprague-Dawley and spontaneously hypertensive rats (SHR). Weanling male Sprague-Dawley and SHR were fed a control (C-Sprague-Dawley, HC-SHR) or a blueberry-enriched (B-Sprague-Dawley, HB-SHR) diet for 8 wks. Aortas were excised and 3mm rings were prepared. After equilibration and preconditioning, rings were precontracted with L-phenylephrine (L-Phe, 3 x 10-7 M). A concentration response curve (CRC) was produced using Acetylcholine (Ach, 10-9 to 3 x 10-6 M), to obtain endothelium-dependent (ED) vasodilation. After a 30 min washout period, a second Ach CRC was obtained in the presence of the inhibitors of nitric oxide (NO) synthase L-NG-methyl-arginate (L-NMMA) (10-4M) and cyclo-oxygenase (COX) mefenamic acid (MFA) (lcrsM). The percent relaxation to the initial precontraction was used to determine vessel sensitivity (pD2) to agonists. A one-way Analysis of Variance test (ANOVA) demonstrated no significant difference in Ach-induced vasodilation (Fmax) between control (C) and blueberry (B) groups in aortas of Sprague-Dawley rats. The NOS inhibition with L-NMMA significantly reduced maximum vasodilation in both treatment groups, with aortas from B group, exhibiting greater decrease of vasodilation (-27% in C and -39% in B aortas). Inhibition of the COX pathway with MFA did not significantly alter the ED vasodilation in response to Ach in either diet group in Sprague Dawley rats. These findings confirm that ED vasodilation in animal model with functional endothelium, such as Sprague-Dawley rats, is mainly mediated through the NO pathway. In the SHR, ED Ach-induced vasodilation was not significantly different between HC and HB aortas. Inhibition of the NOS pathway, significantly reduced maximum vasodilation in both diet groups (- 38% in HC and -34% in HB aortas). Cyclooxygenase (COX) inhibition slightly (not significantly) enhanced ED-vasodilation in HC aortas (101%) but caused a 3% reduced vasodilation in HB aortas, suggesting the presence of vasoconstrictor(s) in HC rats. Thus, blueberries in the SHR may operate through the COX pathway either by reducing the synthesis of vasoconstrictor and/or enhancing the synthesis of vasodilator prostanoids, which may affect NO bioavailability.

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