Altered responses of isolated aortic smooth muscle following chronic ingestion of palm oil diets in rats.

The responsiveness of the rat aorta after chronic consumption of 15% (wt/wt) fresh and thermally oxidized palm oil diets was studied under standard organ bath procedures. Aortic rings from the oxidized oil-fed group showed significantly (P < 0.05) enhanced vascular responses to noradrenaline and potassium chloride when compared with the control and fresh palm oil-fed groups. The maximum tensions were 285.10 +/- 30 mg/mg tissue weight for the oxidized oil-fed group and 148.98 +/- 36 mg/mg for the control in response to noradrenaline. The fresh oil-fed group produced maximum tension of 133.9 +/- 20 mg/mg which was not significantly different from the control. The trend was similar with potassium chloride. The maximum tensions were 206.31 +/- 25 mg/mg for the oxidized oil-fed group and 93.33 +/- 13 mg/mg for the control group. The fresh oil-fed group produced maximum tension of 109.31 +/- 7.8 mg/mg which was not significantly different from the control. Relaxation to acetylcholine was significantly (P < 0.01) attenuated in the aortic rings obtained from the oxidized palm oil-fed group when compared with the control and fresh palm oil-fed groups. The percentage maximum relaxations to acetylcholine were 28.1 +/- 6.7% in the oxidized oil-fed group, 71.4 +/- 6.0% in control and 78.2 +/- 6.0% in the fresh oil-fed groups. The relaxation in the fresh oil-fed group was not significantly different from control. These results suggest that functional changes occur in rat blood vessels after chronic consumption of thermally oxidized palm oil.