Effect of dietarytrans fatty acids on some membrane‐associated enzymes and receptors in rat heart

Abstract

Three groups of male weanling Sprague-Dawley rats were fed diets containing 20% corn oil, 20% partially hydrogenated soybean oil (PHSBO) or 18% PHSBO +2% corn oil. PHSBO contained about 48% of its total fatty acids astrans-octadecenoate. Rats were killed after 16–18 weeks of feeding the various diets, hearts were dissected and crude sarcolemma was prepared by differential centrifugation. The activities of ouabain-sensitive (Na⁺+K⁺)ATPase were significantly lower in membranes of rats fed 20% PHSBO than the control rats fed 20% corn oil. The feeding of 2% corn oil with 18% PHSBO resulted in partial restoration of the enzyme activity. The maximum number of [³H]ouabain-binding sites (B_max) was also lower in cardiac membranes of rats fed 20% PHSBO than those fed 20% corn oil. Similar to (Na⁺+K⁺)ATPase activity, some restoration of the number of [³H]ouabain-binding sites was observed when 2% corn oil was fed with 18% PHSBO-containing diet. There was no difference in the binding affinity of the radioligand for the receptor among the 3 dietary groups. Adenylate cyclase activities (fluoride-, isoproterenol- and forskolinstimulated) were lower in membranes of rats fed 20% PHSBO or 18% PHSBO +2% corn oil than in the control group fed 20% corn oil. Density of the β-adrenergic receptor was the lowest in cardiac membranes of rats fed 20% PHSBO. The feeding of 2% corn oil with 18% PHSBO resulted in partial restoration of the maximum number of [³H]dihydroalprenolol (DHA)-binding sites. The affinity of the binding sites was, however, not affected by the type of the dietary fat. The results of this study suggest that dietarytrans fatty acids can affect the activities of (Na⁺+K⁺)ATPase and adenylate cyclase and the density of digitalis and β-adrenergic receptors in rat heart.