N-3 and N-6 fatty acids modulate the inotropic response to calcium in hypothyroid rat papillary muscle.
The calcium sensitivity of papillary muscles was enhanced at low [Ca2+] in euthyroid rats fed a diet enriched in n-3 fatty acids compared to rats fed diets high in n-6 and saturated (SAT) fatty acids. At the same time, the maximum developed tension was 44% lower in animals fed the n-3 diet compared to those fed the n-6 diet and 62% lower than the rats fed the SAT diet. In hypothyroid animals fed the n-3 diet, the inotropic response to added Ca2+ was only 60% of that in euthyroid controls and 50 and 65% of euthyroid controls in n-6 and SAT diet-fed animals, respectively. Although the response was again lower in n-3-fed animals, the differences among the diet treatments were not as great as those seen in euthyroid animals, and there were no apparent diet-dependent differences in sensitivity to Ca2+ in hypothyroid animals. The potency of the calcium-channel blocker nifedipine was diet-dependent in euthyroid animals, with the order of decreasing sensitivity being n-3 > n-6 > SAT. Papillary muscles were not as sensitive to nifedipine in hypothyroid animals, although n-3-fed animals again showed the greatest inhibition of tension development. On the other hand, nitrendipine-binding affinity was not different among euthyroid and hypothyroid animals fed the n-6 diet.(ABSTRACT TRUNCATED AT 250 WORDS)
Awumey
E M
EM
Department of Oral Biology, University of Alberta, Edmonton, Canada.
Pehowich
D J
DJ
D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002118:Calcium / Q000494:pharmacology*; D004032:Diet; D004042:Dietary Fats, Unsaturated / Q000494:pharmacology*; D015525:Fatty Acids, Omega-3 / Q000494:pharmacology*; D043371:Fatty Acids, Omega-6; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects; D007037:Hypothyroidism / Q000139:chemically induced / Q000503:physiopathology*; D066298:In Vitro Techniques; D008297:Male; D008566:Membranes / Q000187:drug effects; D009200:Myocardial Contraction / Q000187:drug effects*; D009568:Nitrendipine / Q000378:metabolism; D009929:Organ Size / Q000187:drug effects; D010210:Papillary Muscles / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley
D004042:Dietary Fats, Unsaturated; D015525:Fatty Acids, Omega-3; D043371:Fatty Acids, Omega-6; D005231:Fatty Acids, Unsaturated; D009568:Nitrendipine; D002118:Calcium