Metabolism of L-cysteine in rats fed low and high protein diets

L-Cysteine (5.0 mmol per kg of body weight) was intraperitoneally injected into rats fed a 25% casein or 5% casein diet. Concentrations of acidic and neutral amino acids in various tissues were determined 2 h later. In the rats fed the 25% casein diet there was a tendency for tissue amino acid and glutathione levels to be slightly lower than controls. In the 5% casein diet group, however, concentrations of tissue amino acids and glutathione generally increased after L-cysteine administration. S-(2-Hydroxy-2-carboxyethylthio)cysteine (HCETC,3-mercaptolactate-cysteine disulfide), though in trace amounts, was detected in kidney and blood plasma in the 5% casein diet group. Increases in cysteine-glutathione disulfide in liver, kidney and erythrocytes in the 5% casein diet group were considerable. These results indicate that L-cysteine was rapidly metabolized in the 25% casein diet group through the oxidative pathway, while in the 5% casein diet group, in which liver cysteine dioxygenase activity is supposed to be quite low, the oxidative metabolism of L-cysteine decreased and part of the L-cysteine was metabolized through the transaminative pathway. Administration of 15.0 mmol L-cysteine per kg of body weight to rats fed the 25% casein diet resulted in an increase in cysteine-glutathione disulfide in liver, kidney and erythrocytes, and the appearance of HCETC in blood plasma.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of type of protein on food intake of rats fed high protein diets

The effects of type of protein on intake of a high protein diet after adapting rats to a low protein diet were examined in rats trained to eat a 5.2% (N X 6.25) protein diet containing a mixture of casein, lactalbumin, egg white and soy protein, in a single 3-hour period per day. Food intake was measured from 0-15, 15-30, 30-90, and 90-180 minutes. After a 2-week adjustment period, rats were presented with a 40% (N X 6.25) protein purified diet containing only one of the 4 proteins mentioned above or a mixture of these 4 proteins. During the first 15-minute interval, rats eating diets containing protein mixture, lactalbumin, egg white or soy protein depressed their intake significantly compared with the average intake of the 3-day pre-test period, whereas rats eating casein diet increased their intake. During the last 90-minute interval of the first day, all rats depressed their intake, those rats eating casein the least and those rats eating egg white the most. On the second day, rats offered lactalbumin depressed their intake 52.5% for the 3-hour period and rats offered casein depressed their intake 34.3%. Rats eating soy protein, egg white and protein mixture increased their intake from day 1 to day 2. These experiments show that type of protein affects rats' initial intake when they are offered a high protein diet.(ABSTRACT TRUNCATED AT 250 WORDS)     

Phosphate and the development of nephrocalcinosis in rats fed diets containing alpha protein.

It has been suggested that nephrocalcinosis in rats fed diets containing alkali-treated soy protein may be due to a high availability of phosphate in the diet. In the present study, the development of nephrocalcinosis in rats fed a diet containing 20% alpha protein (an alkali-treated soy protein) was compared with that in rats fed the same diet supplemented with additional phosphate. Phosphate supplementation of the alpha protein diet produced a form of nephrocalcinosis that was morphologically different, at both the light- and electronmicroscopic level, from that obtained with the unsupplemented diet but was quite similar to that obtained with a phosphate-supplemented standard commercial laboratory diet. Levels of serum and urinary calcium and phosphorus and urinary cyclic AMP suggested that a phosphate-induced secondary hyperparathyroidism was present in the rats fed either of the phosphate-supplemented diets, but not in the rats fed the unsupplemented alpha protein diet. The results of this study suggest that nephrocalcinosis in rats fed a diet containing 20% alpha protein, without additional phosphate, is not typically phosphate-induced.     

Acute effects of selected hepatotoxic agents on polyribosomes and protein synthesis in the livers of rats fed purified diets containing hepatocarcinogens

This investigation was concerned with the effects of certain hepatocarcinogens ingested for long- or short-term intervals upon selected responses of rat liver to specific hepatotoxic stimuli. Rats fed ad libitum for long (3 to 45 weeks) periods or force-fed for short (3 days) periods purified diets containing a single hepatocarcinogen, ethionine, N-2-fluorenylacetamide, 3′-methyl-4-dimethylaminoazobenzene, or thioacetamide, were subjected to the acute administration of a single hepatotoxic agent, such as puromycin, actinomycin D, sparsomycin, hypertonic NaCl or CCl₄, and hepatic protein synthesis (in vitro) and polyribosomal aggregation were evaluated. Relating to in vitro protein synthesis, in long-term experiments, puromycin induced less inhibition in the experimental groups than in the control (basal diet) group; and actinomycin D inhibited all groups similarly; while in the short-term experiments, puromycin induced less inhibition in the experimental groups than in the control group; actinomycin D inhibited he basal and ethionine groups more than the other groups; sparsomycin induced variable degrees of inhibition, with the ethionine group showing the most and the N-2-fluorenylacetamide and thioacetamide groups showing the least; hypertonic NaCl markedly inhibited all groups similarly; and CCl₄ induced somewhat variable degrees of inhibition, with the thioacetamide group showing less than the other groups. In a few long-term experiments where hepatomas were evaluated in relation to surrounding liver tissue, puromycin administration induced less inhibition in the hepatomas than in the surrounding liver while actinomycin D administration induced similar inhibition in both groups. In general, in all experiments the degree of polyribosomal disagregation was parallel to that of inhibition of protein synthesis (in vitro). The results reveal that the livers of rats fed purified diets containing selected hepatocarcinogens responded in a variable manner in regard to protein synthesis (in vitro) and status of polyribosomal aggregation to the acute administration of selected hepatotoxic agents.     

Effect of pre-feeding ammonium acetate on food intake of rats fed high protein diets

The effect on intake of a 75% casein diet after prefeeding for one week a 6% casein basal diet with additional 0%, 2%, 5%, 8% or 15% ammonium acetate was examined in rats trained to eat in three hours per day. Food intake was measured from 0-15, 15-30, 30-90, and 90-180 minutes for the first two days that the ammonium acetate diets were presented. Rats eating 5% and 8% or 15% ammonium acetate diet depressed their intake significantly for one day and for four days respectively. Rats eating 2%, 5%, 8%, or 15% ammonium acetate diets depressed their intake significantly from 0-30 minutes. When presented with the 75% casein diet, rats prefed 0% to 5% and 8% and 15% ammonium acetate diets ate 55% to 58% and 72% and 94% of their respective baseline intakes. It is suggested that prefeeding 15% ammonium acetate apparently induces sufficient metabolic adaptation to ammonia intake so that the rat is able to offset the metabolic consequences of intake of the 75% casein diet, thus preventing the usual food intake depressing effect of the high protein diet.     

Application of LS 7500 counter (Beckman) for measurement of phagocytosis of 14C labeled bacteria

For determination of phagocytosis of Staphylococcus aureus 519 labeled with glycine-1-14C by guinea pig granulocytes, the third analytical program of LS 7500 counter was used. By measuring isotope radioactivity, the program enables evaluation of the percentage of a bound isotope in relation to the reference sample. In the present experiments the percentage of a bound isotope stands for the percentage of phagocytized bacteria calculated in relation to a reference sample, i.e. to radioactivity of bacteria added to the test. The program applied allows an automatic calculation of the percentage of phagocytized bacteria, the result being printed by a counter printer.     

Arctium lappa ameliorates endothelial dysfunction in rats fed with high fat/cholesterol diets

ABSTRACT: BACKGROUND: Arctium lappa L. (Asteraceae), burdock, is a medicinal plant that is popularly used for treating hypertension, gout, hepatitis, and other inflammatory disorders. This study was performed to test the effect of ethanol extract of Arctium lappa L. (EAL) seeds on vascular reactivity and inflammatory factors in rats fed a high fat/cholesterol diet (HFCD). METHOD: EAL-I (100 mg * kg1/day), EAL-II (200 mg * kg1/day), and fluvastatin (3 mg * kg1/day) groups initially received HFCD alone for 8 weeks, with EAL supplementation provided during the final 6 weeks. RESULTS: Treatment with low or high doses of EAL markedly attenuated plasma levels of triglycerides and augmented plasma levels of high-density lipoprotein (HDL) in HFCD-fed rats. Chronic treatment with EAL markedly reduced impairments of acetylcholine (ACh)-induced relaxation of aortic rings. Furthermore, chronic treatment with EAL significantly lowered systolic blood pressure (SBP) and maintained smooth and flexible intimal endothelial layers in HFCD-fed rats. Chronic treatment with EAL suppressed upregulation of intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1, and E-selectin in the aorta. Chronic treatment with EAL also suppressed increases in matrix metalloproteinase (MMP)-2 expression. These results suggested that EAL can inhibit HFCD-induced vascular inflammation in the rat model. CONCLUSION: The present study provides evidence that EAL ameliorates HFCD-induced vascular dysfunction through protection of vascular relaxation and suppression of vascular inflammation.     

Effects of a soy protein product on serum and tissue cholesterol concentrations in swine fed high-fat, high-cholesterol diets

Hypocholesterolemic effect of a soy protein product was studied in swine fed a high-fat, high-cholesterol diet. In the first experiment, a group of swine were fed 42% butter (by calories) and 1055 mg cholesterol daily, with casein as the source for protein, for 6 weeks and this diet resulted in moderately high serum cholesterol concentrations (219 ± 33 mg/dl). Another group fed the same diet except with soy protein product as the protein source instead of casein showed virtual normocholesterolemia at the end (107 ± 3 mg/dl). Cholesterol balance was studied under non-steady state conditions using methods designed for this purpose. Reflecting the serum cholesterol concentration, the total body cholesterol concentration (excluding CNS) was also significantly lower in soy protein group. However, parameters of cholesterol balance, such as fecal neutral and acidic steroid excretions, dietary cholesterol absorption, and whole body cholesterol synthesis were studied and no differences were demonstrated between the casein- and soy protein-fed swine. The experiment was repeated and in Experiment II virtually the same results were obtained. When swine were given the same high-fat, high-cholesterol diets with $\text{1}\text{2}$ casein + $\text{1}\text{2}$ soy protein or casein + soy protein, hypocholesterolemic effects were also observed. Therefore, such action is probably caused principally by soy protein per se rather than simply by replacement of casein by soy protein. Addition of dl-methionine to soy protein containing diet did not alter the hypocholesterolemic effect of soy protein indicating that the effect was not the result of methionine deficiency. In conclusion, we can state that the hypocholesterolemic action of soy protein was clearly demonstrated in swine fed a high-fat, high-cholesterol diet, but that the mechanism of action is yet to be established.