Effect of dietary polyunsaturated fatty acids on contraction and relaxation of rat femoral resistance arteries.
We investigated the effects of dietary polyunsaturated fatty acids (PUFA) derived from fish oil (n-3 PUFA) and plant seed oil (n-6 PUFA), in amounts relevant to human consumption, on the alpha 1-adrenoceptor-mediated contractile responses of isolated rat resistance arteries. Rats were fed semisynthetic diets, deriving 40% of total calories from fat. The control diet, which had sufficient linoleic acid to prevent essential fatty acid deficiency, had a polyunsaturated/saturated fatty acid (P/S) ratio of 0.3. The n-3 PUFA were given as a daily oral supplement of fish oil. For the n-6 PUFA diet, the proportion of linoleic acid in the diet was increased to obtain P/S ratio of 2.0. Diets were administered for 8 weeks. At the end of the feeding period, second-order branches of the femoral artery (< 300-micros diameter) were mounted in pairs in an isometric myograph, and responses to norepinephrine (NE) 3 nM-10 microM with addition of yohimbine 1 microM and timolol 1 microM were examined. Subsequently, the vessels were preconstricted with NE to 60% of their maximal response and relaxation to acetylcholine 1 nM-0.1 mM was observed. Dietary n-3 PUFA supplements led to attenuation of the contractile responses of isolated resistance arteries (p < 0.01, repeated-measures analysis of variance, ANOVA-RM) versus control. The n-6 PUFA diet did not exert this effect although there was a downward trend. Diet did not affect EC50 values for NE. Neither n-3 nor n-6 PUFA diet influenced relaxation responses. The fatty acid composition of myocardial phospholipid fractions was significantly altered by both diets.(ABSTRACT TRUNCATED AT 250 WORDS)
MacLeod
D C
DC
Cardiovascular Research Unit, University of Edinburgh, Scotland.
Heagerty
A M
AM
Bund
S J
SJ
Lawal
T S
TS
Riemersma
R A
RA
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D004041:Dietary Fats / Q000494:pharmacology*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism / Q000494:pharmacology*; D005263:Femoral Artery / Q000187:drug effects* / Q000502:physiology; D005395:Fish Oils / Q000494:pharmacology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009206:Myocardium / Q000737:chemistry; D009638:Norepinephrine / Q000494:pharmacology; D010743:Phospholipids / Q000032:analysis; D010938:Plant Oils / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013999:Timolol / Q000494:pharmacology; D015016:Yohimbine / Q000494:pharmacology
D004041:Dietary Fats; D005231:Fatty Acids, Unsaturated; D005395:Fish Oils; D010743:Phospholipids; D010938:Plant Oils; D015016:Yohimbine; D013999:Timolol; D000109:Acetylcholine; D009638:Norepinephrine