title: Effects of diabetes and evening primrose oil treatment on responses of aorta, corpus cavernosum and mesenteric vasculature in rats.
abstract: Diabetes causes endothelial dysfunction, with deleterious effects on nitric oxide (NO) mediated vasodilatation. However, in many vessels other local vasodilators such as endothelium-derived hyperpolarizing factor (EDHF), prostacyclin, epoxides or endocannabinoids are also important. Several of these factors may be derived from omega-6 essential fatty acids via arachidonate metabolism. Diabetes inhibits this pathway, a defect that may be bypassed by diets enriched with omega-6 gamma-linolenic acid-containing oils such as evening primrose oil (EPO). The aim was to examine the effects of preventive EPO treatment on endothelium-dependent and neurally mediated vasorelaxation. Diabetes was induced by streptozotocin in rats; duration was 8 weeks. Vascular responses were examined in vitro on thoracic aorta, corpus cavernosum and perfused mesenteric bed preparations. Diabetes caused 25% and 35% deficits, respectively, in aorta and corpus cavernosum NO-mediated endothelium-dependent relaxation to acetylcholine that were largely unaffected by EPO treatment. Moreover, a 44% reduction in maximum corpus cavernosum vasorelaxation to nitrergic nerve stimulation was not prevented by EPO. However, for the mesenteric vascular bed, a 29% diminution of responses to acetylcholine, mediated by both NO and EDHF, was 84% attenuated by EPO treatment. When the EDHF component was isolated during NO synthase inhibition, a 76% diabetic deficit was noted. This was completely prevented by EPO treatment, which also caused supernormal EDHF responses in nondiabetic rats. EPO treatment prevented the development of deficits in endothelium-dependent relaxation in diabetic rats. Effects were particularly marked on the resistance vessel EDHF system, which may have potential therapeutic relevance for diabetic microvascular complications.
authors.affiliation: Department of Biomedical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland, UK.
authors.forename: Alison M
authors.initials: AM
authors.lastname: Jack
authors.forename: Alan
authors.initials: A
authors.lastname: Keegan
authors.forename: Mary A
authors.initials: MA
authors.lastname: Cotter
authors.forename: Norman E
authors.initials: NE
authors.lastname: Cameron
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001013:Aorta, Thoracic / Q000187:drug effects / Q000378:metabolism; D001685:Biological Factors / Q000494:pharmacology; D001786:Blood Glucose / Q000378:metabolism; D063385:Cannabinoid Receptor Modulators; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D005228:Fatty Acids, Essential / Q000494:pharmacology*; D066298:In Vitro Techniques; D008041:Linoleic Acids; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D031665:Oenothera biennis; D010413:Penis / Q000187:drug effects*; D010656:Phenylephrine / Q000494:pharmacology; D010938:Plant Oils; D051381:Rats; D013152:Splanchnic Circulation / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D017965:gamma-Linolenic Acid
chemical_list: D000970:Antineoplastic Agents; D001685:Biological Factors; D001786:Blood Glucose; D063385:Cannabinoid Receptor Modulators; D005228:Fatty Acids, Essential; D008041:Linoleic Acids; D010938:Plant Oils; D014662:Vasoconstrictor Agents; C067410:endothelium-dependent hyperpolarization factor; D010656:Phenylephrine; C028498:evening primrose oil; D017965:gamma-Linolenic Acid