Restoration of depressed prostanoid-induced ileal contraction in spontaneously hypertensive rats by dietary fish oil

We have reported that dietary fish oil (FO) rich in n−3 PUFA modulates gut contractility. It was further demonstrated that the gut of spontaneously hypertensive rats (SHR) has a depressed contractility response to prostaglandins (PG) compared with normotensive Wistar-Kyoto (WKY) rats. We investigated whether feeding diets supplemented with n−3 PUFA increased gut contractility and restored the depressed prostanoid response in SHR gut. Thirteen-week-old SHR were fed diets containing fat at 5 g/100 g as coconut oil (CO), lard, canola oil containing 10% (w/w) n−3 FA as α-linolenic acid (18∶3n−3), or FO (as HiDHA®, 22∶6n−3) for 12 wk. A control WKY group was fed 5 g/100 g CO in the diet. As confirmed, the SHR CO group had a significantly lower gut response to PGE2 and PGF2α compared with the WKY CO group. Feeding FO increased the maximal contraction response to acetylcholine in the ileum compared with all diets and in the colon compared with lard, and restored the depressed response to PGE2 and PGF2α in the ileum but not the colon of SHR. FO feeding also led to a significant increase in gut total phospholipid n−3 PUFA as DHA (22∶6n−3) with lower n−6 PUFA as arachidonic acid (20∶4n−6). Canola feeding led to a small increase in ileal EPA (20∶5n−3) and DHA and in colonic DHA without affecting contractility. However, there was no change in ileal membrane muscarinic binding properties due to FO feeding. This report confirms that dietary FO increases muscarinic- and eicosanoid receptor-induced contractility in ileum and that the depressed prostanoid response in SHR ileum, but not colon, is restored by tissue incorporation of DHA as the active nutrient.