High Concentrations Of Arginine Research Articles

Screening of amino acids as a safe energy source for isolated rat pancreatic acini.

Amino acids play an essential role in protein synthesis, metabolism and survival of pancreatic acini. Adequate nutritional support is important for acute pancreatitis treatment. However, high concentrations of arginine and lysine may induce acute pancreatitis. The study aimed to identify the most suitable L-amino acids as safe energy sources for pancreatic acinar cells. Pancreatic acini were isolated from male Wistar rats. Effects of amino acids (0.1-20 mM) on uncoupled respiration of isolated acini were studied with a Clark electrode. Cell death was evaluated with fluorescent microscopy and DNA gel electrophoresis. Among the tested amino acids, glutamate, glutamine, alanine, lysine and aspartate were able to stimulate the uncoupled respiration rate of isolated pancreatic acini, while arginine, histidine and asparagine were not. Lysine, arginine and glutamine (20 mM) caused complete loss of plasma membrane integrity of acinar cells after 24 h of incubation. Glutamine also caused early (2-4 h) cell swelling and blebbing. Aspartate, asparagine and glutamate only moderately decreased the number of viable cells, while alanine and histidine were not toxic. DNA fragmentation assay and microscopic analysis of nuclei showed no evidence of apoptosis in cells treated with amino acids. Alanine and glutamate are safe and effective energy sources for mitochondria of pancreatic acinar cells.

Melatonin Mediates Axillary Bud Outgrowth by Improving Nitrogen Assimilation and Transport in Rice.

Melatonin plays an important role in plant resistance to biotic and abiotic stresses. However, whether melatonin is involved in the regulation of plant architecture, such as the formation of axillary bud outgrowth or tillering, in rice remains unknown. Here, we found that different concentrations of melatonin influenced axillary bud outgrowth in rice, and moderate melatonin concentrations also alleviated the inhibition of axillary bud outgrowth in the presence of high concentrations of basic amino acids lysine and arginine. Furthermore, transcriptome analysis demonstrated that genes involved in nitrogen metabolism and phytohormone signal transduction pathways may affect axillary bud outgrowth, which is regulated by melatonin. We determined that the differentially expressed genes glutamine synthetase OsGS2 and amino acid transporter OsAAP14, which are involved in nitrogen metabolism and are regulated by melatonin and basic amino acids, were the key regulators of axillary bud outgrowth in rice. In addition, we validated the functions of OsGS2 and OsAAP14 using rice transgenic plants with altered axillary bud outgrowth and tillers. Taken together, these results suggest that melatonin mediates axillary bud outgrowth by improving nitrogen assimilation and transport in rice.

Molecular and neuronal mechanisms for amino acid taste perception in the Drosophila labellum

Amino acids are essential nutrients that act as building blocks for protein synthesis. Recent studies in Drosophila have demonstrated that glycine, phenylalanine, and threonine elicit attraction, whereas tryptophan elicits aversion at ecologically relevant concentrations. Here, we demonstrated that eight amino acids, including arginine, glycine, alanine, serine, phenylalanine, threonine, cysteine, and proline, differentially stimulate feeding behavior by activating sweet-sensing gustatory receptor neurons (GRNs) in L-type and S-type sensilla. In turn, this process is mediated by three GRs (GR5a, GR61a, and GR64f), as well as two broadly required ionotropic receptors (IRs), IR25a and IR76b. However, GR5a, GR61a, and GR64f are only required for sensing amino acids in the sweet-sensing GRNs of L-type sensilla. This suggests that amino acid sensing in different type sensilla occurs through dual mechanisms. Furthermore, our findings indicated that ecologically relevant high concentrations of arginine, lysine, proline, valine, tryptophan, isoleucine, and leucine elicit aversive responses via bitter-sensing GRNs, which are mediated by three IRs (IR25a, IR51b, and IR76b). More importantly, our results demonstrate that arginine, lysine, and proline induce biphasic responses in a concentration-dependent manner. Therefore, amino acid detection in Drosophila occurs through two classes of receptors that activate two sets of sensory neurons in physiologically distinct pathways, which ultimately mediates attraction or aversion behaviors.

Coordinated action of multiple transporters in the acquisition of essential cationic amino acids by the intracellular parasite Toxoplasma gondii.

Intracellular parasites of the phylum Apicomplexa are dependent on the scavenging of essential amino acids from their hosts. We previously identified a large family of apicomplexan-specific plasma membrane-localized amino acid transporters, the ApiATs, and showed that the Toxoplasma gondii transporter TgApiAT1 functions in the selective uptake of arginine. TgApiAT1 is essential for parasite virulence, but dispensable for parasite growth in medium containing high concentrations of arginine, indicating the presence of at least one other arginine transporter. Here we identify TgApiAT6-1 as the second arginine transporter. Using a combination of parasite assays and heterologous characterisation of TgApiAT6-1 in Xenopus laevis oocytes, we demonstrate that TgApiAT6-1 is a general cationic amino acid transporter that mediates both the high-affinity uptake of lysine and the low-affinity uptake of arginine. TgApiAT6-1 is the primary lysine transporter in the disease-causing tachyzoite stage of T. gondii and is essential for parasite proliferation. We demonstrate that the uptake of cationic amino acids by TgApiAT6-1 is 'trans-stimulated' by cationic and neutral amino acids and is likely promoted by an inwardly negative membrane potential. These findings demonstrate that T. gondii has evolved overlapping transport mechanisms for the uptake of essential cationic amino acids, and we draw together our findings into a comprehensive model that highlights the finely-tuned, regulated processes that mediate cationic amino acid scavenging by these intracellular parasites.

Longitudinal associations of physical activity with plasma metabolites among colorectal cancer survivors up to 2\xa0years after treatment

We investigated longitudinal associations of moderate-to-vigorous physical activity (MVPA) and light-intensity physical activity (LPA) with plasma concentrations of 138 metabolites after colorectal cancer (CRC) treatment. Self-reported physical activity data and blood samples were obtained at 6 weeks, and 6, 12 and 24 months post-treatment in stage I-III CRC survivors (n = 252). Metabolite concentrations were measured by tandem mass spectrometry (BIOCRATES AbsoluteIDQp180 kit). Linear mixed models were used to evaluate confounder-adjusted longitudinal associations. Inter-individual (between-participant differences) and intra-individual associations (within-participant changes over time) were assessed as percentage difference in metabolite concentration per 5 h/week of MVPA or LPA. At 6 weeks post-treatment, participants reported a median of 6.5 h/week of MVPA (interquartile range:2.3,13.5) and 7.5 h/week of LPA (2.0,15.8). Inter-individual associations were observed with more MVPA being related (FDR-adjusted q-value < 0.05) to higher concentrations of arginine, citrulline and histidine, eight lysophosphatidylcholines, nine diacylphosphatidylcholines, 13 acyl-alkylphosphatidylcholines, two sphingomyelins, and acylcarnitine C10:1. No intra-individual associations were found. LPA was not associated with any metabolite. More MVPA was associated with higher concentrations of several lipids and three amino acids, which have been linked to anti-inflammatory processes and improved metabolic health. Mechanistic studies are needed to investigate whether these metabolites may affect prognosis.

Selection for Growth and Precocity Alters Muscle Metabolism in Nellore Cattle.

To clarify the relationship between beef genetic selection for growth and precocity with muscle metabolism and metabolites, we performed metabolomic analysis using Longissimus lumborum (LL) muscle from Nellore cattle with divergent selection for these traits (high growth, HG; low growth, LG; high precocity, HP; low precocity, LP). Genetic potential for growth affected muscle protein and energetic metabolism. HG animals had a high concentration of arginine, carnosine, and leucine compared to LG animals. HP animals presented a high concentration of glutamine, betaine, creatinine, isoleucine, carnitine, acetyl carnitine, and lower levels of glucose compared to LP animals, affecting protein and fatty acid metabolism. Intensity of selection (high or low) was correlated with changes in protein metabolism, and the type of selection (growth or precocity) affected fat metabolism. In conclusion, both HG and HP appear to be correlated with a high concentration of protein metabolites and changes in protein metabolic pathways, while selection for precocity is more correlated with changes in fat metabolism compared to animals selected for growth.

Nitric oxide homeostasis is required for light-dependent regulation of conidiation in Aspergillus

Nitric oxide (NO) can be biologically synthesized from nitrite or from arginine. Although NO is involved as a signal in many biological processes in bacteria, plants, and mammals, still little is known about the role of NO in fungi. Here we show that NO levels are regulated by light as an environmental signal in Aspergillus nidulans. The flavohaemoglobin-encoding fhbB gene involved in NO oxidation to nitrate, and the arginine-regulated arginase encoded by agaA, which controls the intracellular concentration of arginine, are both up-regulated by light. The phytochrome fphA is required for the light-dependent induction of fhbB and agaA, while the white-collar gene lreA acts as a repressor when arginine is present in the media. The intracellular arginine pools increase upon induction of both developmental programs (conidiation and sexual development), and the increase is higher under conditions promoting sexual development. The presence of low concentrations of arginine does not affect the light-dependent regulation of conidiation, but high concentrations of arginine overrun the light signal. Deletion of fhbB results in the partial loss of the light regulation of conidiation on arginine and on nitrate media, while deletion of fhbA only affects the light regulation of conidiation on nitrate media. Our working model considers a cross-talk between environmental cues and intracellular signals to regulate fungal reproduction.

Contribution of ROS and metabolic status to neonatal and adult CD8+ T cell activation.

In neonatal T cells, a low response to infection contributes to a high incidence of morbidity and mortality of neonates. Here we have evaluated the impact of the cytoplasmic and mitochondrial levels of Reactive Oxygen Species of adult and neonatal CD8+ T cells on their activation potential. We have also constructed a logical model connecting metabolism and ROS with T cell signaling. Our model indicates the interplay between antigen recognition, ROS and metabolic status in T cell responses. This model displays alternative stable states corresponding to different cell fates, i.e. quiescent, activated and anergic states, depending on ROS levels. Stochastic simulations with this model further indicate that differences in ROS status at the cell population level contribute to the lower activation rate of neonatal, compared to adult, CD8+ T cells upon TCR engagement. These results are relevant for neonatal health care. Our model can serve to analyze the impact of metabolic shift during cancer in which, similar to neonatal cells, a high glycolytic rate and low concentrations of glutamine and arginine promote tumor tolerance.

Arginine-enveloped virus inactivation and potential mechanisms.

Arginine synergistically inactivates enveloped viruses at a pH or temperature that does little harm to proteins, making it a desired process for therapeutic protein manufacturing. However, the mechanisms and optimal conditions for inactivation are not fully understood, and therefore, arginine viral inactivation is not used industrially. Optimal solution conditions for arginine viral inactivation found in the literature are high arginine concentrations (0.7-1 M), a time of 60 min, and a synergistic factor of high temperature (≥40°C), low pH (≤pH 4), or Tris buffer (5 mM). However, at optimal conditions full inactivation does not occur over all enveloped viruses. Enveloped viruses that are resistant to arginine often have increased protein stability or membrane stabilizing matrix proteins. Since arginine can interact with both proteins and lipids, interaction with either entity may be key to understanding the inactivation mechanism. Here, we propose three hypotheses for the mechanisms of arginine induced inactivation. Hypothesis 1 describes arginine-induced viral inactivation through inhibition of vital protein function. Hypothesis 2 describes how arginine destabilizes the viral membrane. Hypothesis 3 describes arginine forming pores in the virus membrane, accompanied by further viral damage from the synergistic factor. Once the mechanisms of arginine viral inactivation are understood, further enhancement by the addition of functional groups, charges, or additives may allow the inactivation of all enveloped viruses in mild conditions.

MRNA dynamics and alternative conformations adopted under low and high arginine concentrations control polyamine biosynthesis in Salmonella

mRNA dynamics and alternative conformations adopted under low and high arginine concentrations control polyamine biosynthesis in Salmonella

MRNA dynamics and alternative conformations adopted under low and high arginine concentrations control polyamine biosynthesis in Salmonella.

Putrescine belongs to the large group of polyamines, an essential class of metabolites that exists throughout all kingdoms of life. The Salmonella speF gene encodes an inducible ornithine decarboxylase that produces putrescine from ornithine. Putrescine can be also synthesized from arginine in a parallel metabolic pathway. Here, we show that speF expression is controlled at multiple levels through regulatory elements contained in a long leader sequence. At the heart of this regulation is a short open reading frame, orf34, which is required for speF production. Translation of orf34 interferes with Rho-dependent transcription termination and helps to unfold an inhibitory RNA structure sequestering speF ribosome-binding site. Two consecutive arginine codons in the conserved domain of orf34 provide a third level of speF regulation. Uninterrupted translation of orf34 under conditions of high arginine allows the formation of a speF mRNA structure that is degraded by RNase G, whereas ribosome pausing at the consecutive arginine codons in the absence of arginine enables the formation of an alternative structure that is resistant to RNase G. Thus, the rate of ribosome progression during translation of the upstream ORF influences the dynamics of speF mRNA folding and putrescine production. The identification of orf34 and its regulatory functions provides evidence for the evolutionary conservation of ornithine decarboxylase regulatory elements and putrescine production.

Evaluation of genetically-improved (glandless) and genetically-modified low-gossypol cottonseed meal as alternative protein sources in the diet of juvenile southern flounder Paralichthys lethostigma reared in a recirculating aquaculture system

Cottonseed meal (CSM) proteins from genetically-improved (glandless) low-gossypol seed (GI-CSM, 52.1% crude protein, CP), genetically-modified low-gossypol seed (GMO-CSM, 56.0% CP) and from an untreated regular (glanded) seed (R-CSM 49.9% CP) were evaluated to replace fish meal (FM) protein (59.5% CP) in juvenile southern flounder Paralichthys lethostigma diets. Eight isonitrogenous (45% CP) and isolipidic (16% crude lipid, CL) diets were formulated. A control diet (0% CSM) contained 40% fishmeal (FM) and other practical protein sources. Six diets replaced 50, 75 and 100% FM protein with GI-CSM or GMO-CSM protein. One diet replaced 100% FM protein by R-CSM protein. Fifteen fish (mean = 1.81 g) were stocked in each of twenty-four 75-L tanks (N = 3 per treatment) and were fed the treatment diets for eight weeks. Final percent weight gain was not significantly (P > 0.05) different in fish fed the GI- and GMO- and R-CSM protein diets (898–1405%) compared with the control diet (0% CSM) (1242%), but percent weight gain was greater (P < 0.05) in fish fed the 50% GI-CSM diet (1405%) versus the 100% GI-CSM diet (898%). Feed conversion ratio was excellent for all treatments (FCR = 0.70–1.00), with no treatment differences (P < 0.05). Protein efficiency ratios (PER) were also not significantly different among the treatments (2.26–3.24), although the lowest value was for 100% R-CSM diets. After 8 weeks of feeding, survival of fish ranged from 80 to 91%, with no treatment differences. Apparent protein digestibility of diets was significantly higher for the fish fed 75% and 100% GI-CSM and 100% GMO-CSM protein diets (83.5, 83.5 and 86.5%, respectively) compared with the control diet (79.4%). After 8 weeks, no significant (P > 0.05) interactive effects between CSM sources and FM replacement levels on final weight, FCR and PER were observed. Arginine levels in the diets increased as CSM was increased, consistent with the high arginine concentrations found in CSM. Liver gossypol was only detectable in fish fed the 100% R-CSM diet (37 μg/g). Replacing up to 75% FM protein by GI- or GMO-CSM protein did not affect on whole body omega-3 PUFAs, or liver gossypol. The results suggest that up to 75% of fish meal protein may be replaced by GI- or GMO-CSM protein in the diet of juvenile flounder without adverse effects on growth performance and body composition. Statement of relevanceCottonseed meal (CSM) is a potentially cost-effective alternative plant protein source for use in aquafeeds. The results suggest that a 75% of fishmeal protein could be replaced by genetically-improved and genetically modified (GMO) low gossypol based cottonseed flour protein in the diet of southern flounder. These ultra-low gossypol cottonseed flour proteins could be inexpensive protein sources for the commercial culture of southern flounder and other finfish species.

Functional evaluation of yuzu (Citrus junos) extracts containing limonoids and polyamine for life extension

We determined high concentrations of arginine and polyamines (putrescine, spermidine, and spermine) in yuzu (Citrus junos) seeds. Yuzu produces large quantities of limonoids. We fed limonoid aglycones extracted from yuzu seeds and commercial spermine asa polyamine to Sandhoff disease (SD) mice with abnormal glycolipid metabolism and autosomal recessive inheritance, as found in humans. Ingestion of limonoid aglycones and spermine by SD mice extended their longevity by about 10–12%, where it alleviated inflammation of the central nervous system. After administering limonoid aglycones or limonoid aglycones/spermine, analyses of the bacterial flora in the feces based on 16S rDNA indicated changes in the relative ratio between Bacteroidetes (Bacteroidales and Lactobacillus) and Firmicutes (Clostridiales and Erysipelotrichaceae). In both SD and wild-type mice, the amount of short-chain fatty acids produced by the bacterial flora increased according to the intake of limonoid aglycones and spermine.

Heterologous expression of an active chitin synthase from Rhizopus oryzae

Chitin synthases are highly important enzymes in nature, where they synthesize structural components in species belonging to different eukaryotic kingdoms, including kingdom Fungi. Unfortunately, their structure and the molecular mechanism of synthesis of their microfibrilar product remain largely unknown, probably because no fungal active chitin synthases have been isolated, possibly due to their extreme hydrophobicity. In this study we have turned to the heterologous expression of the transcript from a small chitin synthase of Rhizopus oryzae (RO3G_00942, Chs1) in Escherichia coli. The enzyme was active, but accumulated mostly in inclusion bodies. High concentrations of arginine or urea solubilized the enzyme, but their dilution led to its denaturation and precipitation. Nevertheless, use of urea permitted the purification of small amounts of the enzyme. The properties of Chs1 (Km, optimum temperature and pH, effect of GlcNAc) were abnormal, probably because it lacks the hydrophobic transmembrane regions characteristic of chitin synthases. The product of the enzyme showed that, contrasting with chitin made by membrane-bound Chs’s and chitosomes, was only partially in the form of short microfibrils of low crystallinity. This approach may lead to future developments to obtain active chitin synthases that permit understanding their molecular mechanism of activity, and microfibril assembly.

Arginine and proline applied as food additives stimulate high freeze tolerance in larvae of Drosophila melanogaster.

The fruit fly Drosophila melanogaster is an insect of tropical origin. Its larval stage is evolutionarily adapted for rapid growth and development under warm conditions and shows high sensitivity to cold. In this study, we further developed an optimal acclimation and freezing protocol that significantly improves larval freeze tolerance (an ability to survive at -5°C when most of the freezable fraction of water is converted to ice). Using the optimal protocol, freeze survival to adult stage increased from 0.7% to 12.6% in the larvae fed standard diet (agar, sugar, yeast, cornmeal). Next, we fed the larvae diets augmented with 31 different amino compounds, administered in different concentrations, and observed their effects on larval metabolomic composition, viability, rate of development and freeze tolerance. While some diet additives were toxic, others showed positive effects on freeze tolerance. Statistical correlation revealed tight association between high freeze tolerance and high levels of amino compounds involved in arginine and proline metabolism. Proline- and arginine-augmented diets showed the highest potential, improving freeze survival to 42.1% and 50.6%, respectively. Two plausible mechanisms by which high concentrations of proline and arginine might stimulate high freeze tolerance are discussed: (i) proline, probably in combination with trehalose, could reduce partial unfolding of proteins and prevent membrane fusions in the larvae exposed to thermal stress (prior to freezing) or during freeze dehydration; (ii) both arginine and proline are exceptional among amino compounds in their ability to form supramolecular aggregates which probably bind partially unfolded proteins and inhibit their aggregation under increasing freeze dehydration.

Amino acid profile of collagen fractions extracted from by-products of Ophistonema libertate and Scomber japonicus

The objective of this study was to identify the amino acid profile (AAp) of collagen extracted from Ophistonema libertate and Scomber japonicus head:tail homogenates. Salt (SSC)-, acid (ASC)-, and pepsin (PSC)-soluble collagens and insoluble collagen (IC) were extracted by solubility. The homogenates of both species exhibited high concentrations of proline, aspartic acid, glutamic acid, arginine, histidine, and hydroxyproline. Higher concentrations of aspartic acid and lysine were registered in S. japonicus SSC compared with O. libertate. S. japonicus PSC showed significantly higher concentrations for most of the amino acids (AAs) evaluated compared with O. libertate, including aspartic acid, glutamic acid, serine, glycine, alanine, tyrosine, proline, hydroxyproline, arginine, threonine, methionine, valine, phenylalanine, isoleucine, leucine, lysine, and histidine. Hydroxyproline showed no significant differences among both species homogenates; however, O. libertate IC was higher than S. japonicus IC. Differences detected in the AAp of both species could suggest different properties of the collagen extracted.

Mechanism study of high browning degree of mantle muscle meat from Japanese common squid Todarodes pacificus during air-drying

Mantle meat from the Japanese common squid (Todarodes pacificus) browns more than other squid meats during air-drying. The factors contributing to the browning of Japanese common squid, long-finned squid (Photololigo edulis) and bigfin reef squid (Sepioteuthis lessoniana) were studied in boiled and raw meat both before and after air-drying. Dried raw meat from the Japanese common squid browned more than dried boiled meat (b∗ value, from 4.7 to 28.5). The results from SDS–PAGE showed significant degradation of myosin heavy chain (MHC) suggesting that protease activity in raw Japanese common squid meat was higher than in the other two species. The concentration of arginine (1932.0mg/100g) and ribose (28.8μmol/g) in Japanese common squid meat was higher than in the other two species. These results suggest that high protease activity and high concentrations of arginine and ribose increase the browning discoloration of Japanese common squid during air-drying.

Activity and characterization of mixed organic compounds extracted from Rhodobacter sphaeroides as alternative materials to serum for mammalian cell growth

Photosynthetic microorganisms produce relatively large amounts of physiologically active materials which stimulate the physiological activity of other organisms. In this study, mammalian HeLa cells were cultured in different culture media which were Dulbecco's modified Eagle medium (DMEM) with newborn calf serum (NCS), and DMEM including different types of physiologically activating compounds (PACs) extracted from Rhodobacter sphaeroides grown under various culture conditions. R. sphaeroides was grown under the following five different culture conditions: anaerobically in the light, anaerobically in the dark and treated with dimethyl sulfoxide, aerobically in the dark for 48 h, in the light for 48 h, and in the light for 24 h and changed after previous culturing in the dark for 24 h. The growth of HeLa cell was measured by cell counting using a hemocytometer, and the fluorescent intensities of cellular lysosomes were measured to check the level of cellular stress caused by adding PACs. The growth of HeLa cells cultured in DMEM with PACs extracted from R. sphaeroides aerobically grown under dark conditions was enhanced compared to that of cells grown with NCS. We also found that a high concentration of pigments such as bacteriochlorophylls and carotenoids and a high concentration of arginine produced by R. sphaeroides aerobically grown in the dark were implicated in increased growth of the HeLa cells. Therefore, our results suggest that PACs extracted from R. sphaeroides aerobically cultured in dark conditions can enhance the physiological activity of mammalian cells and serve as nontoxic and bioavailable materials.

Regulation of Arginine Acquisition and Virulence Gene Expression in the Human Pathogen Streptococcus pneumoniae by Transcription Regulators ArgR1 and AhrC

In this study, we investigated for the first time the transcriptional response of the human pathogen Streptococcus pneumoniae to fluctuating concentrations of arginine, an essential amino acid for this bacterium. By means of DNA microarray analyses, several operons and genes were found, the expression of which was affected by the concentration of arginine in the medium. Five of the identified operons were demonstrated to be directly repressed in the presence of high arginine concentrations via the concerted action of the ArgR-type regulators ArgR1 and AhrC. These ArgR1/AhrC targets encompass the putative amino acid transport genes artPQ, abpA, abpB, and aapA; the arginine biosynthetic genes argGH; and the virulence genes aliB and lmB/adcAII-phtD encoding an oligopeptide-binding lipoprotein and cell surface Zn(2+)-scavenging units, respectively. In addition, the data indicate that three of the amino acid transport genes encode an arginine ATP-binding cassette transporter unit required for efficient growth during arginine limitation. Instead of regulating arginine biosynthetic and catabolic genes as has been reported for other Gram-positive bacteria, our findings suggest that the physiological function of ArgR1/AhrC in S. pneumoniae is to ensure optimal uptake of arginine from the surrounding milieu.

The Effect of Pumpkin (&lt;i&gt;Cucurbita pepo&lt;/i&gt; L) Seeds and L-Arginine Supplementation on Serum Lipid Concentrations in Atherogenic Rats

The present study aimed to examine the effect of pumpkin (Cucurbita pepo L.) seeds supplementation on atherogenic diet-induced atherosclerosis. Rat were divided into two main groups , normal control and atherogenic control rats , each group composed of three subgroups one of them supplemented with 2% arginine in drinking water and the other supplemented with pumpkin seeds in diet at a concentration equivalent to 2% arginine. Supplementation continued for 37 days. Atherogenic rats supplemented with pumpkin seeds showed a significant decrease (p<0.001) in their serum concentrations of total cholesterol and LDL - C as they dropped from 4.89 mmol / L to 2.55 mmol /L and from 3.33 mmol / L to 0.70 mmol / L respectively. Serum concentrations of HDL-C were also significantly elevated in the same group. Although, atherogenic rats supplemented with 2% arginine showed significant increase in serum concentration of HDL-C, no significant changes were observed in their serum concentrations of total cholesterol and LDL-C. Our results showed that treatment of atherogenic rats with pumpkin seeds significantly decreased serum concentrations of TC and LDL-C. Our findings suggest that pumpkin seeds supplementation has a protective effect against atherogenic rats and this protective effect was not attributed to the high arginine concentrations in pumpkin seeds.