(³H)Forskolin‐ and (³H)dihydroalprenolol‐binding sites and adenylate cyclase activity in heart of rats fed diets containing different oils

Abstract

The characteristics of the cardiac adenylate cyclase system were studied in rats fed diets containing fish oil (menhaden oil) and other oils. Adenylate cyclase activity generally was higher in cardiac homogenates and membranes of rats fed diet containing 10% menhaden oil than in the other oils. The increase in enzyme activity, especially in forskolin‐stimulated activity, was associated with an increase in the concentration of the [3H]forskolin‐binding sites in cardiac membranes of rats fed menhaden oil. The β‐adrenergic receptor concentration was not significantly altered although the affinity for [3H]dihydroalprenolol‐binding was lower in membranes of rats fed menhaden oil than those fed the other oils. ω‐3 fatty acids from menhaden oil were incorporated into the cardiac membrane phospholipids. The results suggest that the observed increase in myocardial adenylate cyclase activity of rats fed menhaden oil may be due to an increase in the number of the catalytic subunits of the enzyme or due to a greater availability of the forskolin‐binding sites.

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

“…The initial (13 wk) and final (25 wk) weights (g) of the experimental animal groups as mean ± SEM (n) were as follows: WKY CO, 276 ± 6, 414 ± 8 (12); SHR CO, 290 ± 5, 427 ± 8 (16); SHR SF, 294 ± 4, 419 ± 4 (16); SHR Can, 307 ± 5, 417 ± 4 (16); and SHR FO, 308 ± 4, 428 ± 6 (16). There was no significant difference between weights for WKY or SHR CO groups or between final or ∆ (final minus initial) weights between SHR dietary groups.…”

“…The final pellet was resuspended in (mmol/L) 50 Tris, 1 EGTA, 10 MgCl 2 , pH 7.4 assay buffer that contained protease inhibitors diluted into this buffer at 1:1000 (vol/vol). The stock protease inhibitor concentrations were (mg/mL, solvent): phenylmethylsulfonyl fluoride 17.4, DMSO; aprotinin 1, H 2 O; iodoacetate 184, H 2 O; and pepstatin A 1.37, DMSO (16). The final tissue concentration was approximately 5 mg/mL, and the stock solution was stored in aliquots at −80°C for muscarinic binding assays.…”

“…Receptor radio-ligand binding activity was determined in the gut membrane fraction (6,000-50,000 × g) with the nonselective tritiated muscarinic antagonist, quinuclidinyl benzylate ([ 3 H]QNB) (16). For saturation binding assays, membranes (approximately 100 µg protein/tube) were incubated with shaking in assay buffer with increasing concentrations of [ 3 H]QNB (specific activity 1.6 TBq/mmol; NEN, Sydney Australia) (0.05-2 nmol/L) at 30°C for 1 h. Preliminary experiments performed in triplicate (not shown) established that [ 3 H]QNB binding to the gut membrane preparation was linear between 20 and 200 µg protein and that at 100 µg protein per assay, maximal binding occurred by 40 min.…”

Lipids, Membrane Receptors, and Enzymes: Effects of Dietary Fatty Acids

“…Modification of membranes by manipulation of lipid composition in vitro or an vivo by different dietary fatty acids can alter the activity of important intrinsic enzymes, eg, adenyl cyclase, 5'-nucleotidase, and Ca-ATPase. [53][54][55][56] Hormonally activated adenyl cyclase, which catalyzes the formation of cAMP, is comprised of a receptor for the hormone (glucagon in liver, PGE2 in cardiac membranes, dopamine in brain), a membrane G protein transducer element, and the catalytic unit, adenyl cyclase. The three components are asymmetrically arranged in plasma membrane of liver and in the absence of agonist the three components can move independently laterally.…”

Cross‐influence of membrane polyunsaturated fatty acids and hypoxia‐reoxygenation on α‐ and β‐adrenergic function of rat cardiomyocytes

“…Such changes were reported to influence the contraction rate and the systolic ejection volume of the rat heart and improve the metabolic recovery and oxygen consumption after ischemia and reperfusion (4,5). In addition, dietary PUFA appeared to influence the cardiac noradrenaline sensitivity through alteration of the receptor binding characteristics and the signalling pathway (6)(7)(8), although differences in methodological approaches led to discordant data (9,10). Less attention has been devoted to the specific effect of PUFA on sarcolemmal protein function in pathological conditions.…”