The temporal effect of a wild blueberry (Vaccinium angustifolium)-enriched diet on vasomotor tone in the Sprague-Dawley rat

Background and aims: We have previously reported that wild blueberry (Vaccinium angustifolium)-enriched diets (WB) attenuate aortic adrenergic response through endothelial-mediated pathways. The duration of dietary intervention necessary to induce the positive changes on vasomotor tone has not been studied to date. Thus, our objective was to investigate the temporal effect of WB consumption on vascular function and reactivity in Sprague-Dawley (SD) rat aorta after 4 and 7 weeks of dietary treatment. Methods and results: Forty male SD rats were randomly assigned to a control (AIN-93) (C) or a WB diet for 4 or 7 weeks. Vascular ring studies were conducted in 3-mm isolated rat aortic rings to investigate vasoconstriction induced by six doses of the alpha(1)- adrenergic agonist, L-phenylephrine (Phe, 10(-8)-3 x 10(-6) M) alone or in the presence of the NOS inhibitor, L-N-G-monomethyl-arginine (L-NMMA, 10(-4) M). The maximum force of contraction (F-max) and vessel sensitivity (pD(2)) were determined. Analysis of variance revealed no significant differences on Fmax after 4 weeks of the WB diet but only a significant increase in pD(2) in the absence of L-NMMA. Seven week WB consumption significantly attenuated contraction in response to L-Phe and resulted in lower pD(2). Inhibition of NOS induced a significant increase in the constrictor response in both diet groups at both time periods, with the WB group fed for 7 weeks having the greater response. Conclusion: Thus wild blueberries incorporated into the diet at 8% w/w positively affect vascular smooth muscle contractility and sensitivity but these effects are evident only after 7 weeks of WB consumption.