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

Abstract

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 alpha-linolenic acid (1 8:3n-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 PGF2alpha 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 PGF2alpha 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.

Interactive Effects of Dietary Resistant Starch and Fish Oil on Short-Chain Fatty Acid Production and Agonist-Induced Contractility in Ileum of Young Rats

“…The present study confirms previous findings (12,23) in adult rats that the feeding of fish oil supplemented diets to weaned rats leads to increased incorporation of n-3 PUFA into ileal phospholipids at the expense of monounsaturated and n-6 PUFA. Both diets supplemented with 10% tuna fish oil rich in DHA resulted in approximately 12% n-3 PUFA in ileal tissue total phospholipid, mainly as DHA.…”

“…Both diets supplemented with 10% tuna fish oil rich in DHA resulted in approximately 12% n-3 PUFA in ileal tissue total phospholipid, mainly as DHA. In a previous experiment with only 5% fish oil with the same FA profile, there was over 10% as n-3 PUFA with no EPA detected and virtually all n-3 PUFA as DHA (23). From this study, we also confirm that increased membrane n-3 PUFA as DHA correlates with increased ileal contractility owing to muscarinic and eicosanoid agonists.…”

“…In our recent study with spontaneously hypertensive rats, there was no increase in the number or sensitivity of muscarinic receptors in fractionated ileal muscle tissue after fish oil supplementation using a nonspecific labeled muscarinic antagonist, [3H]-QNB (23). In the present study using 10-week-old rats and specific muscarinic receptor subtype inhibitors, the rank-order potency for muscarinic subtypes using contracting isolated ileal tissue was M 3 > M 1 > M 2 .…”

“…Unlike muscarinic and isoprostane responses, the PGE 2 and PGF 2α effects in young rats appeared to be much lower than the response in older rats (9,13,23). This blunted response was greatly enhanced by n-3 PUFA from fish oil and with fish oil plus RS.…”

“…This blunted response was greatly enhanced by n-3 PUFA from fish oil and with fish oil plus RS. A depressed prostanoid response has recently been reported by our laboratory for spontaneously hypertensive rats (14) that by dietary fish oil supplementation was reversed in ileum but not colon, even though ileum and colon incorporated similar proportions of n-3 PUFA into the total phospholipid pools (23). It is to be determined if this prostanoid defect occurs at the receptor or postreceptor level.…”