EFFECTS OF DIETARY SPIRULINA-MAXIMA ON VASOMOTOR RESPONSES OF AORTA RINGS FROM RATS FED A FRUCTOSE-RICH DIET

The effects of dietary Spirulina on vasomotor responses of aorta rings from male Wistar rats fed a purified fructose-rich diet were analyzed . For this purpose, the animals were allocated to one of three groups. Group A received 60% glucose, group B received 60% fructose and group C received, in addition to 60% fructose, 5% Spirulina. All animals we re fed (20g/day/rat) the experimental diets for six weeks. Vasomotor r esponses were evaluated by concentration-response (CR) curves to pheny lephrine (PE) and to carbamoylcholine (CCh) of aorta rings with and wi thout endothelium. Rings with endothelium from fructose-fed rats devel oped more tension in response to PE and relaxed significantly less in response to CCh than corresponding rings from rats of group A. In the former rings, indomethacin-induced inhibition of cyclooxygenase decrea sed significantly the PE-induced tension development and enhanced sign ificantly the CCh-induced relaxation. Rings with endothelium from rats of group C showed, relative to corresponding rings from group B, a ri ghtward shift of the CR curve to PE and a significant decrease in the maximum PE-induced tension development. In comparison to rings with en dothelium from group B, corresponding rings from group C showed both a significant leftward shift of the CR curve to CCh and a significant i ncrease in the maximum percent of the CCh-induced relaxation. No signi ficant differences were observed in the CR curves to these agonists of rings without endothelium from either group. These results suggest th at dietary fructose increases both the basal and the muscarinic recept or-mediated synthesis/release of some cyclooxygenase-dependent vasocon stricting metabolites of arachidonic acid. These data also suggest, th at dietary Spirulina is able to prevent these effects of fructose. (C) 1998 Elsevier Science Inc.