Tissue Selenium in Pigs with Dietetic Microangiopathy (MAP, “Mulberry Heart”)

Mean selenium contents of liver, heart muscle and skeletal muscle of pigs with dietetic microangiopathy (MAP), but without waxy muscle degeneration (MD) and hepatosis diaetetica (HD), were 1113, 850 and 265 ng/g d.s., respectively. These values were not lower than corresponding values of control pigs without MAP, MD and HD.     

The role of vitamin E in the body

The basic experimental data obtained at the Department of Coenzymes' Biochemistry of the A. V. Palladin Institute of Biochemistry of the Ukr. SSR Academy of Sciences as to the biological role of vitamin E are analyzed. Vitamin E, selenium and methionine are found to induce peculiar changes in the activity of glutathione-peroxidase, metabolism of sulphur-containing amino acids, biosynthesis of adenine nucleotides, proteins and nucleic acids. Participation of alpha-tocopherol and its active derivatives in the control of biosynthesis and intertransformation of ubiquinone and its cyclic isomer, ubichromenol, in the animal organism, is proved, which determines to a considerable extent the biological role of vitamin E in the bioenergy processes. It is substantiated in experiments that the detected wide range of the biological effect of vitamin E is associated with the control of RNA biosynthesis. Under these conditions the effect of vitamin E on the RNA synthesis does not depend on the manifestation of antioxidant properties of its molecule and in this sense it is a specific one. The results obtained are discussed for their significance in explanation of the molecular mechanism of the vitamin E action and in substantiation of the possibility to use the results in practical medicine and animal husbandry.     

Effect of Dietary Fat Quality and Vitamin E on the Antioxidant Potential of Pigs

A randomized blocked factorial experiment was conducted with 90 young pigs. From 4 to 11 weeks of age the pigs were kept in individual pens and fed a selenium supplemented basal diet consisting mostly of propionic acid treated barley, soybean meal and dried skim milk, and containing < 0.5 mg vitamin E per kg. The treatment factors during this period were 3 dietary levels of added vitamin E (nil, 10 and 30 mg/kg) and a 6 % supplement of fresh or oxidized fat (2/3 lard and 1/3 herring oil). From 11 weeks of age until slaughter at 90 kg the pigs received the vitamin E supplements but no fat or dried skim milk. The basal diet for this later experimental period was based on untreated dry barley. Blood samples collected during the period of investigation were examined for vitamin E and for resistance against erythrocyte lipid peroxidation (ELP) in order to evaluate the antioxidant status. Analysis of variance and Student’s t-test on least squares means showed the ELP to be influenced independently by the vitamin E supplement and, during the fat feeding period, by the quality of the fat supplement, with the highest peroxidation resistance (low ELP) in the groups fed fresh fat and a high level of vitamin E. Blood vitamin E level was only influenced — positively — by the vitamin E supplement although variations in the feed vitamin E level below 10–15 mg vitamin E per kg did not result in corresponding variations in measurable blood vitamin E concentrations. In the same low range of vitamin E in the feed there was a statistically significant difference in ELP values between the different vitamin E treatment groups. No clinical manifestations of selenium-vitamin E deficiency were observed in the pigs. The ELP and the plasma vitamin E levels observed would seem to suggest that a total of 15 mg vitamin E per kg barley-based feed will not always be sufficient for growing pigs.     

Nutritive value of leaf-protein concentrate from potato haulm for rats and chicks

A leaf-protein concentrate (LPC), containing approximately 45% protein, was prepared from potato haulm by standard methods. Its content of essential amino acids was similar to that recommended for chicken diets, except for the sulphur-containing amino acids, especially cystine. The biological value estimated in rats was high (64), almost as high as that of soya protein (65), but its true digestibility was lower (82 and 91, respectively). The concentrate contained carotenoids (295 mg/kg), but these were not converted into vitamin A in chicks. Leaf-protein concentrate may be a usable protein source for chicks, provided that not more than 25% of it is included in their diet.     

Etiologic factors and pathologic alterations in selenium-vitamin E deficiency and excess in animals and humans

The etiology of selenium-vitamin E (Se-E) deficiency diseases may be complex. Many of the syndromes involve combined deficiency of selenium and vitamin E. Selenium moves into the animal and human food chain from soil and plants, which may contain inadequate amounts of the nutrient in many areas of the world. Vitamin E may be in low concentration in many animal feeds unless supplements are added. Some syndromes, such as steatitis in cats, result from an increased requirement of vitamin E in diets that contain large amounts of polyunsaturated fatty acids, and these diseases will only respond to vitamin E administration. Deficiency syndromes in animals owing to pure Se deficiency are infrequent and have been produced mainly by laboratory studies utilizing extreme deficiency conditions. Other factors that may affect the occurrence of these deficiency diseases are concurrent dietary deficiency of S-containing amino acids, bioavailability of different forms of dietary Se, intake of compounds that antagonize Se (e.g., silver salts), and exposure to various prooxidant substances (e.g., iron compounds, oxygen, ozone, and various drugs). A wide variety of pathologic alterations occur in animals and humans with Se-E deficiency. Myocardial lesions are seen most frequently in calves, lambs, pigs, turkey poults, and ducklings. In humans, Keshan disease, an endemic cardiomyopathy in China, is attributed to Se deficiency. Necrosis of skeletal muscle is the most frequent lesion observed in animal species. Necrosis of smooth muscle of the gizzard and intestine may be a prominent lesion in turkey poults, ducklings, and quail. Other Se-E deficiency lesions include hepatic necrosis, gastric ulceration, intestinal and uterine lipofuscinosis, pancreatic damage, steatitis, exudative diathesis, encephalomalacia, and testicular necrosis. Selenium toxicosis is well characterized in animals and humans by neurological, hoof, and hair alterations.     

Influence of Diet on Experimental Swine Dysentery. 1. Effects of A Vitamin E and Selenium Deficient Diet Supplemented with 6.8 % Cod Liver Oil

Sixteen growing pigs were fed a vitamin E and selenium deficient diet; half of the animals (Group 2) were given a daily supply of vitamin E and selenium. After having been fed these diets for 53 days, the pigs were infected orally with minced colonic material from cases with typical swine dysentery. This exposure resulted in outbreaks of swine dysentery in both groups. The incubation times were, however, distinctly shorter and the clinical symptoms much more pronounced in Group 1 than in Group 2. The patho^morphological lesions in the colon also differed between the 2 groups. In the pigs of Group 1 evident pseudomembraneous lesions were observed in the spiral colon. In Group 2, the colonic alterations consisted predominantly of a catarrhal enteritis; pseudomembranes occurred in a minor part of colon in only 4 pigs. Both the clinical and the chemical observations and the pathological findings indicated a much better vitamin E and selenium balance in the pigs of Group 2. It is concluded that the treatment with vitamin E and selenium in Group 2 greatly increased resistance to swine dysentery.     

Interacting nutritional and infectious etiologies of Keshan disease

In 1979, Chinese scientists reported that selenium had been linked to Keshan disease, an endemic juvenile cardiomyopathy found in China. However, certain epidemiological features of the disease could not be explained solely on the basis of inadequate selenium nutrition. Fluctuations in the seasonal incidence of the disease suggested involvement of an infectious agent. Indeed, a coxsackievirus B4 isolated from a Keshan disease victim caused more heart muscle damage when inoculated into selenium-deficient mice than when given to selenium-adequate mice. Those results led us to study the relationship of nutritional status to viral virulence. Coxsackievirus B3/0 (CVB3/0), did not cause disease when inoculated into mice fed adequate levels of Se and vitamin E. However, mice fed diets deficient in either Se or vitamin E developed heart lesions when infected with CVB3/0. To determine if the change in viral phenotype was maintained, we passaged virus isolated from Se-deficient hosts, maintained, we passaged virus isolated from Se-deficient hosts, designated as CVB3/0 Se-, back into Se-adequate hosts. The CVB3/0 Se- virus caused disease in Se-adequate mice. To determine if the phenotype change was due to changes in the viral genome, we sequenced viruses isolated from Se-deficient mice and compared them with the input CVB3/0 virus. Six point mutations differed between the parent strain and the recovered CVB3/0 Se- isolates. When the experiment was repeated using vitamin E-deficient mice, the same 6 point mutations were found. This is the first report of a specific host nutritional deficiency altering viral genotype. Keshan disease may be the result of several interacting causes including a dominant nutritional deficiency (selenium), other nutritional factors (vitamin E, polyunsaturated fatty acids), and an infectious agent (virus).     

Evaluation of vitamin E requirement and food palatability in rabbits fed a purified diet with a high fish oil content

The vitamin E requirement of rabbits fed a semi-synthetic diet containing high amounts of fish oil was studied. Three groups of 5 rabbits were fed fish oil diets containing, respectively, 50, 100 and 500 mg/kg vitamin E. Moreover diet palatability was evaluated by using different levels of grass meal: 0.5, 1 and 2%, respectively. Incorporation of 1% grass meal in the diet was sufficient to achieve acceptance of the fish oil diet. Increased vitamin E intake resulted in a dose-related rise in vitamin E levels in serum, blood platelets, liver and adipose tissue. The higher vitamin E intake was reflected by a twofold increase of vitamin E in serum, platelets and adipose tissue, and a tenfold increase in the liver. The adipose tissue revealed histopathological changes of yellow fat disease, mainly in the low-dose vitamin E group. In the liver microgranulomas of lipofuscin-laden macrophages were seen. Vitamin E was found to decrease but not to prevent the formation of these lesions. The results indicate that protection of marine oils against in vivo oxidation is problematic in the rabbit. It is questionable whether in this animal vitamin E is an adequate biological anti-oxidant for very long chain n-3 fatty acids.     

Clinico-Pathologic Findings in Young Pigs Fed Different Levels of Selenium,Vitamin E and Antioxidant

A randomized, blocked 23 factorial experiment was conducted with 48 young pigs. The treatment factors were: 2 levels of selenium (55 and 115 µg/kg), 2 levels of vitamin E (3 and 53 mg/kg) and 2 levels of the antioxidant feed additive Ethoxyquin (0 and 150 mg/kg). All pigs were kept in single pens and fed ad libitum throughout the experimental period of 9 weeks, i.e. from 3 to 12 weeks of age. Plasma, heart, liver and muscle Se levels as well as whole blood glutathione peroxidase activity (EC 1.11.1.9 GSH-Px) were significantly higher in pigs given a dietary supplement of Se than in pigs given no supplement of Se (P ≤ 0.001). The Se-supplemented pigs showed a tendency to lower mean serum transaminase activity (ASAT and ALAT) than unsupplemented pigs, but the influence was significant (P ≤ 0.05) only for the ALAT activity. Blood vit. E levels were higher for pigs receiving a supplement of vit. E than for unsupplemented pigs (P ≤ 0.001), and so was the resistance of red blood cells against lipid peroxidation (ELP), as expressed by lower ELP values. There were no effects of Ethoxyquin supplementation on the biochemical variables included in the study. The histological examination of heart muscle showed that the score for changes was negatively influenced by both Se and vit. E supplement (P ≤ 0.001) and to some extent also by Ethoxyquin supplement (P ≤ 0.05). The histological picture of m. long dorsi was influenced only by the vit. E supplement (P ≤ 0.01). No histological changes were found in the liver in this study. There were inverse relationships between whole blood GSH-Px defluorescence time and blood Se, and between ELP and whole blood vit. E (P ≤ 0.001).     

A Cloned Pig Model for Examining Atherosclerosis Induced by High Fat,High Cholesterol Diets

The pig is a recognized model for the onset of coronary heart disease and heart attacks. Previous studies have shown that serum cholesterol levels in the pig can be elevated using a high fat, high cholesterol (HFHC) diet. What has been lacking is a genetically defined model corresponding to human ApoE4 susceptibility that can be linked to diets capable of inducing atherosclerosis. This study used a cloned pig model to examine the impact of cholesterol levels with the development of aorta fatty deposits leading to atherosclerosis. Diets were formulated using vegetable sources of protein to provide similar intakes of metabolizable energy, calcium, phosphorous and principal amino acids in both control and HFHC groups. After 60 days, the HFHC group demonstrated a 40-fold increase in aortic fatty streak lesion area combined with 6- and 11-fold increases in total and LDL cholesterol, respectively, over control diet fed cloned pigs. Previous studies have suffered from either imbalanced total caloric intake, an overall imbalance in the nutrition of the control versus HFHC groups or genetic heterogeneity when evaluating dietary constraints related to atherosclerosis. This study demonstrated that cloned, genetically-defined ApoE4 pigs provided balanced nutrition diets provide an experimental system ideally suited to examining atherosclerosis and the onset of coronary heart disease.     

Vitamin E, Selenium, Trolox C, Ascorbic Acid Palmitate, Acetylcysteine, Coenzyme Q, β-Carotene, Canthaxanthin, and (+)-Catechin Protect Against Oxidative Damage to Kidney, Heart, Lung and Spleen

Male Sprague-Dawley rats were fed diets that varied qualitatively and quantitatively in antioxidants. Kidney, heart, lung, and spleen homogenates were incubated at 37°C with and without hydroperoxide or Fe⁺². Protection of antioxidants against oxidative damage to tissue was determined by measurement of oxidized heme proteins. Tissues from rats supplemented with dietary vitamin E and selenium showed protection compared to tissues from rats on the basal diet. Tissues from rats with diets containing larger quantities of antioxidants and both fat soluble antioxidants: vitamin E, β-carotene, coenzyme Q₁₀, ascorbic acid 6-palmitate and water soluble antioxidants: selenium, trolox C, acetylcysteine, coenzyme Q₀, (+)-catechin, showed the highest protection.     

荷叶离褶伞子实体营养成分分析与评价

经测定,荷叶离褶伞Lyophyllum decastes子实体含粗蛋白21.4%,粗脂肪8.2%,粗纤维9.52%,碳水化合物53.03%,灰分13.6%;必需氨基酸6.02g/100g,占氨基酸总量(16.82g/100g)的35.78%;含维生素B10.068mg、维生素B24.26mg、维生素B6590μg、维生素B1255.7μg、烟酸21.2mg;1kg子实体含锌50.0mg、铜19.0mg、硒0.013mg、镉1.85mg、汞0.56mg、铅0.75mg、砷0.29mg。     

Combined Therapeutic Effect of Dietary Selenium and Vitamin Ε on Manifested Vesd Syndrome in Weaned Pigs

By using a therapeutic dietary supplementation in pigs, which had developed the vitamin Ε and selenium deficiency (VESD) syndrome, the same amounts of α-tocopheryl acetate and selenium were found to be effective as under prophylactic conditions. The experiment thus supported the conclusions that the addition of 5 mg DL-α-tocopheryl acetate/kg and 135 μg selenium/kg to a diet, which contained only traces of vitamin Ε and selenium, represents a level of minimal requirement. Glutathione peroxidase activity in blood serum was used to evaluate the selenium status in pigs. A modified method for determination of tocopherol in fat tissue was described. The addition of 15 mg α-tocopheryl acetate/kg diet was demonstrated to be sufficient to maintain the tocopherol stores in body fat at an unchanged level.     

Effect of microbial phytase on apparent ileal amino acid digestibility of phosphorus-adequate diets in growing pigs

Six ileally cannulated pigs (mean initial body weight 34.8 kg) were used to study the effect of microbial phytase on apparent ileal digestibility of P, total N and amino acids. Three P-adequate diets (digestible P concentration 2.3 g kg(- )l) containing barley (B), soyabean meal (S) or a mixture of the two (BS) with or without phytase supplement (1000 FTU x kg(-1)) were fed to pigs using a 6 x 6 Latin square design. The addition of phytase increased (p < 0.05) apparent ileal P digestibility of diets B, S and BS by 16.5, 19.2 and 19.2%, respectively. There was no effect of phytase on the ileal digestibility of total N. Apparent ileal digestibility of amino acids tended to increase in the BS diet supplemented with phytase (mean improvement of 2.2%); but no significant difference was found for any amino acid as compared with the unsupplemented diet. To asses the additivity of apparent amino acid digestibility, the determined values for the BS diet were compared to those calculated from digestibilities found in diets B and S. There were no significant differences between the determined and calculated values. It is concluded that the addition of microbial phytase to P-adequate diets does not affect ileal amino acid digestibility in growing pigs and that the apparent amino acid digestibility values determined in single ingredients may be additive when included into a complex diet.     

Both Dietary Supplementation with Monosodium L-Glutamate and Fat Modify Circulating and Tissue Amino Acid Pools in Growing Pigs,but with Little Interactive Effect

Background

The Chinese population has undergone rapid transition to a high-fat diet. Furthermore, monosodium L-glutamate (MSG) is widely used as a daily food additive in China. Little information is available on the effects of oral MSG and dietary fat supplementation on the amino acid balance in tissues. The present study aimed to determine the effects of both dietary fat and MSG on amino acid metabolism in growing pigs, and to assess any possible interactions between these two nutrients.

Methods and Results

Four iso-nitrogenous and iso-caloric diets (basal diet, high fat diet, basal diet with 3% MSG and high fat diet with 3% MSG) were provided to growing pigs. The dietary supplementation with fat and MSG used alone and in combination were found to modify circulating and tissue amino acid pools in growing pigs. Both dietary fat and MSG modified the expression of gene related to amino acid transport in jejunum.

Conclusions

Both dietary fat and MSG clearly influenced amino acid content in tissues but in different ways. Both dietary fat and MSG enhance the absorption of amino acids in jejunum. However, there was little interaction between the effects of dietary fat and MSG.     

Nutritional factors affecting quantity and quality of carcass fat in chickens.

Nonpathological fattening of a bird occurs when the amount of energy consumed exceeds its requirements for maintenance and growth. Dietary energy and protein levels, particularly the ratio of these two, are the main dietary factors affecting fatness. Consumption of diets low in protein results in excess energy intake and an increased hepatic lipogenesis. Excess protein has the opposite effect. It also increases the energy expenditure required to dispose of excess amino acids in the body. Severe deficiency of a specific amino acid does not increase fattening. The degree of fattening, particularly of the liver, induced by corticosterone injection is greater in birds fed diets containing a wide energy-to-protein ratio in comparison to a narrow ratio. The content of dietary fat per se does not affect carcass fat concentration although it alters the rate of liver fatty acid synthesis. The dietary fatty acid composition affects the composition of tissue fatty acids. Consumption of diets containing vegetable oils or high in protein increases the degree of unsaturation of tissue fat and thereby its susceptibility to oxidation. Dietary dl-alpha-tocopheryl acetate increases the stability of the lipids of adipose and muscle tissue of chicks with relatively saturated body fat, but the dietary effectiveness of this vitamin in improving the stability of tissues of birds having relatively unsaturated fat is limited.     

Evolutionary aspects of omega-3 fatty acids in the food supply

Information from archaeological findings and studies from modern day hunter-gatherers suggest that the Paleolithic diet is the diet we evolved on and for which our genetic profile was programmed. The Paleolithic diet is characterized by lower fat and lower saturated fat intake than Western diets; a balanced intake of omega-6 and omega-3 essential fatty acids; small amounts of trans fatty acids, contributing less than 2% of dietary energy; more green leafy vegetables and fruits providing higher levels of vitamin E and vitamin C and other antioxidants than today's diet and higher amounts of calcium and potassium but lower sodium intake. Studies on the traditional Greek diet (diet of Crete) indicate an omega-6/omega-3 ratio of about 1/1. The importance of a balanced ratio of omega-6:omega-3, a lower saturated fatty acid and lower total fat intake (30-33%), along with higher intakes of fruits and vegetables leading to increases in vitamin E and C, was tested in the Lyon Heart study. The Lyon study, based on a modified diet of Crete, confirmed the importance of omega-3 fatty acids from marine and terrestrial sources, and vitamin E and vitamin C, in the secondary prevention of coronary heart disease, and cancer mortality.     

Meat meal in the diet of the early-weaned pig IV. The supplementation of diets with tryptophane,lysine and methionine

Two experiments were conducted with 72 pigs between 28 and 56 days of age to study the effect of tryptophane supplementation on their performance when fed on diets containing wheat and meat meal.In the first experiment, pigs were fed on a basal diet (Diet 1) or on the same diet supplemented with calcium dihydrogen phosphate (Diet 2), bone meal (Diet 3) or bone meal plus tryptophane (Diet 4), all to 3.1% calcium. The weight gains of the pigs (315 g day^?1) fed on Diet 3 were significantly lower than that of the pigs fed on the other three diets (363 g day^?1). The feed conversion ratios showed a similar trend. Diet 3 contained 0.16% tryptophane while the other diets contained 0.18–0.19% tryptophane. The crude protein, lysine and methionine contents of all diets were similar.In the second experiment, a basal diet containing meat meal and bone meal was supplemented with tryptophane, lysine plus methionine or all three amino acids. Feed intake was increased by all amino acid supplements. Weight gains were improved significantly (57%) by the addition of all three amino acids to the diets, but the improvements due to tryptophane alone (28%) or methionine plus lysine (35%) were not significant. Tryptophane supplementation alone or with lysine plus methionine increased the nitrogen retention of the pigs.It was concluded that the requirement for tryptophane of pigs between 28 and 56 days of age was greater than 0.16% of diets containing wheat and meat meal.     

Effects of balancing crystalline amino acids in diets containing heat-damaged soybean meal or distillers dried grains with solubles fed to weanling pigs

Two experiments were conducted to investigate if adjustments in diet formulations either based on total analysed amino acids or standardized ileal digestible (SID) amino acids may be used to eliminate negative effects of including heat-damaged soybean meal (SBM) or heat-damaged corn distillers dried grains with solubles (DDGS) in diets fed to weanling pigs. In Experiment 1, four corn–SBM diets were formulated. Diet 1 contained non-autoclaved SBM (315 g/kg), and this diet was formulated on the basis of analysed amino acid concentrations and using SID values from the AminoDat® 4.0 database. Diet 2 was similar to Diet 1 in terms of ingredient composition, except that the non-autoclaved SBM was replaced by autoclaved SBM at 1 : 1 (weight basis). Diet 3 was formulated using autoclaved SBM and amino acid inclusions in the diet were adjusted on the basis of analysed total amino acid concentrations in the autoclaved SBM and published SID values for non-autoclaved SBM (AminoDat® 4.0). Diet 4 also contained autoclaved SBM, but the formulation of this diet was adjusted on the basis of analysed amino acids in the autoclaved SBM and SID values that were adjusted according to the degree of heat damage in this source of SBM. Pigs (160; initial BW: 10.4 kg) were allotted to the four treatments with eight replicate pens per treatment in a randomized complete block design. Diets were fed to pigs for 21 days. The gain to feed ratio (G : F) was greater (P<0.05) for pigs fed Diet 1 compared with pigs fed the other diets and pigs fed Diet 4 had greater (P<0.05) G : F than pigs fed Diet 2. In Experiment 2, 144 pigs (initial BW: 9.9 kg) were allotted to four diets with eight replicate pens per diet. The four diets contained corn, SBM (85 g/kg) and DDGS (220 g/kg), and were formulated using the concepts described for Experiment 1, except that heat-damaged DDGS, but not heat-damaged SBM, was used in the diets. Pigs fed Diet 1 had greater (P<0.05) G : F than pigs fed Diet 2, but no differences were observed for G : F among pigs fed diets containing autoclaved DDGS. Results demonstrate that the negative effects of heat damage of SBM or DDGS may be ameliorated if the reduced concentration and digestibility of amino acids in heat-damaged SBM or DDGS is taken into account in diet formulation. Further research is needed to improve the prediction of the ileal digestibility of amino acids in heat-processed ingredients used in practical diet formulations.     

The interaction of dietary fatty acid and cholesterol on catecholamine-stimulated adenylate cyclase activity in the rat heart

Diets supplemented with high levels of saturated or unsaturated fatty acids supplied by addition of sheep kidney fat or sunflower seed oil, respectively, were fed to rats with or without dietary cholesterol. The effects of these diets on cardiac membrane lipid composition, catecholamine-stimulated adenylate cyclase and beta-adrenergic receptor activity associated with cardiac membranes, were determined. The fatty acid-supplemented diets, either with or without cholesterol, resulted in alterations in the proportion of the (n-6) to (n-3) series of unsaturated fatty acids, with the sunflower seed oil increasing and the sheep kidney fat decreasing this ratio, but did not by themselves significantly alter the ratio of saturated to unsaturated fatty acids. However, cholesterol supplementation resulted in a decrease in the proportion of saturated and polyunsaturated fatty acids and a dramatic increase in oleic acid in cardiac membrane phospholipids irrespective of the nature of the dietary fatty acid supplement. The cholesterol/phospholipid ratio of cardiac membrane lipids was also markedly increased with dietary cholesterol supplementation. Although relatively unaffected by the nature of the dietary fatty acid supplement, catecholamine-stimulated adenylate cyclase activity was significantly increased with dietary cholesterol supplementation and was positively correlated with the value of the membrane cholesterol/phospholipid ratio. Although the dissociation constant for the beta-adrenergic receptor, determined by [125I](-)-iodocyanopindolol binding, was unaffected by the nature of the dietary lipid supplement, the number of beta-adrenergic receptors was dramatically reduced by dietary cholesterol and negatively correlated with the value of the membrane cholesterol/phospholipid ratio. These results indicate that the activity of the membrane-associated beta-adrenergic/adenylate cyclase system of the heart can be influenced by dietary lipids particularly those altering the membrane cholesterol/phospholipid ratio and presumably membrane physico-chemical properties. In the face of these dietary-induced changes, a degree of homeostasis was apparent both with regard to membrane fatty acid composition in response to an altered membrane cholesterol/phospholipid ratio, and to down regulation of the beta-adrenergic receptor in response to enhanced catecholamine-stimulated adenylate cyclase activity.