High Arginase Activity Research Articles

Arginine metabolism in cat kidney.

1. Arginine is essential for growth in the kitten and, because of the resulting hyperammonaemia, in the adult cat an arginine-free diet is life threatening. 2. The kidney is the main site of arginine synthesis. 3. This study was performed to determine whether the cat kidney synthesizes arginine and to establish which factors, such as low citrullinaemia, defects of argininosuccinate synthase and lyase activities or high renal arginase activity, might limit renal arginine production. 4. Identified nephron segments were isolated by microdissection from collagenase-treated cat kidney. 5. Arginine metabolism was studied by incubating the nephron segments with either physiological concentrations of L-[ureido-14C]citrulline (anabolism) or L-[guanido-14C]-arginine (catabolism). Arginine and urea were measured by a micro-enzymatic method. Amino acids were measured by HPLC. 6. In cat blood, the citrulline, but not the arginine, concentration was very low by comparison with other species. 7. Arginine synthesis occurred almost entirely in the proximal tubule, the highest rate occurring in the proximal convoluted tubule and the lowest in the medullary straight proximal tubule. 8. Arginase activity was restricted to the proximal tubule. Urea production increased from the convoluted towards the medullary straight tubule. 9. The limited capacity of the cat kidney to produce arginine in vivo may result from the low blood concentration of citrulline and from the high arginase activity in the various proximal cells with the ability to synthesize arginine.

Arginine metabolism in experimental glomerulonephritis: interaction between nitric oxide synthase and arginase.

L-Arginine is metabolized by two pathways: 1) by nitric oxide synthase (NOS) to nitric oxide (NO) and 2) by arginase forming urea and L-ornithine. Inflammatory responses may involve a balance between the pathways, as NO is cytotoxic and vasodilatory and L-ornithine is a promoter of cell proliferation and matrix synthesis. In experimental glomerulonephritis we have previously shown that NOS is activated in nephritic glomeruli. We have now examined both pathways of L-arginine metabolism to study competition for L-arginine, temporal variation, and the sources of NOS and arginase. Acute in situ glomerulonephritis was induced in rats, and glomeruli were studied at 1, 4, and 7 days. Both NOS and arginase activities were present. There was temporal variation: NOS activity was highest on day 1 and arginase activity on day 4; both declined by day 7. Competition between the pathways was demonstrated by increased urea synthesis in the presence of NG-monomethyl-L-arginine, an inhibitor of NOS. Measurement of NOS and arginase activities in macrophages isolated from nephritic glomeruli showed that these cells were a major source of glomerular NOS but not arginase activity. In contrast, high arginase activity but low NO production was identified in cultured rat glomerular mesangial cells. These studies show differential temporal variation in expression of NOS and arginase pathways of arginine metabolism in experimental glomerulonephritis. We have found two factors that may contribute to this: 1) competition for substrate L-arginine between the two pathways and 2) different cellular sources. We hypothesize that the balance between these pathways is a mechanism regulating injury, hemodynamics, and mesangial cell proliferation.

Can arginine and ornithine support gut functions?

Arginine and ornithine are precursors of nitric oxide and polyamines, respectively. These metabolites intimately participate in permeability and adaptive responses of the gut. The liver possesses high arginase activity as an intrinsic part of urea synthesis and would consume most of the portal supply of dietary arginine. The gut reduces this possibility by converting dietary arginine to citrulline, which effectively bypass the liver and is resynthesized to arginine in the kidney. Dietary ornithine supplementation, in the form of ornithine alpha-ketoglutarate (OKG) can be considered as an arginine precursor. Several supplement studies have shown both amino acids to promote growth hormone and insulin secretion with anabolic effects in postoperative patients. Their intermediary metabolites (for example, glutamine, proline) may also be of benefit in trauma metabolism. Specific effects of either amino acid on the gut are poorly reported. One recent animal study showed improved morphology after OKG administration, perhaps through increased polyamine secretion. Generation of nitric oxide from arginine has two facets. Excess production from high dose arginine potentiated the effects of experimentally induced sepsis, whereas low doses improved survival. These considerations suggest that the role of enteral diet supplementation with arginine or OKG should be urgently examined for any benefits it may have on mucosal barrier function.

Prostaglandin E2 downregulates Kupffer cell production of IL-1 and IL-6 during hepatic regeneration

The mammalian liver possesses the ability to regenerate to its original size after a 70% partial hepatectomy (PHx). The capacity of rat Kupffer cells (KC) isolated at specific intervals after PHx to produce interleukin (IL)-1, IL-6, and prostaglandin E2 (PGE2) in response to endotoxin [lipopolysaccharide (LPS)] stimulation was evaluated in standard RPMI 1640 (1,200 microM L-arginine) and arginine-depleted RPMI 1640 (< 10 microM L-arginine) media. Because KC function in an environment in which high arginase activity results in negligible L-arginine levels, the 10 microM L-arginine RPMI 1640 was used to simulate the hepatic microenvironment. Regenerating liver KC 12-120 h after PHx responded to LPS with a significantly greater (P < 0.05) production of IL-1 and IL-6 in standard RPMI 1640. This enhancement of regenerating liver KC to produce IL-1 and IL-6 was increased (P < 0.05) by placing these same KC in 10 microM arginine RPMI 1640 culture media. During the same time period, regenerating liver KC produced significantly elevated (P < 0.01) PGE2, again with greater differences in the low-arginine media. In vivo KC PGE2 blockade by indomethacin (5 mg/kg) significantly (P < 0.05) inhibited hepatic regeneration. When the cyclooxygenase inhibitor indomethacin (10 microM) was added to cultures, the production of PGE2 by KC was prevented, and in arginine-depleted cultures, IL-1 and IL-6 production was upregulated (P < 0.05). We conclude that during hepatic regeneration, KC IL-1 and IL-6 production is elevated and is controlled in an autoregulatory fashion by elevated KC PGE2 production.

Arginase is a major pathway of L-arginine metabolism in nephritic glomeruli

L-arginine can be metabolized to nitric oxide (NO) by nitric oxide synthase (NOS) and to urea and L-ornithine by arginase. Competition between these pathways for L-arginine in inflammatory sites has been suggested. In experimental glomerulonephritis glomeruli produce nitrite; a major source is macrophages. We hypothesized that arginase is present in glomeruli and may compete for substrate with NOS in glomerulonephritis. Therefore we examined both pathways in isolated nephritic glomeruli and peritoneal macrophages. Arginase activity was present in glomeruli, increased by > 500% in nephritic glomeruli compared to controls, and was predominant over NOS. Activity increased with L-NMMA (a NOS inhibitor), but this trend did not reach statistical significance. In macrophages both pathways were present; NOS predominated basally but this was reversed by L-NMMA. In contrast with glomeruli macrophage arginase activity increased after LPS stimulation. Levels of macrophage arginase activity could not account for activity in nephritic glomeruli, suggesting another source of arginase. This is the first demonstration of high arginase activity of nephritic glomeruli. Competition between arginase and NOS pathways suggests a regulatory mechanism of L-arginine metabolism within the glomerulus, with implications for the pathogenesis of injury and scarring in glomerulonephritis.

Arginase, a new marker of mammary carcinoma

Activities of arginase, alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase were determined in sera obtained in a group of healthy women, women with verified carcinoma of the breast, benign mastopathy, a group of patients with carcinoma of various organs and a group of patients with acute viral hepatitis. Preoperative values of serum arginase activity in patients with breast carcinoma were up to 4-fold those found in healthy women. Sensitivity of the test was 86%. After the surgery, the activity decreased abruptly during the first week and normalised within 15–30 days. In benign diseases of the breast, the activity of arginase was normal. Serum arginase activity is raised in both benign and malignant liver diseases, however, the quotients alanine aminotransferase/arginase, aspartate aminotransferase/arginase and alkaline phosphatase/arginase differ significantly. Thus, use of alanine aminotransferase/arginase quotient implies a high degree of confidence in differentiating between increased arginase activity in mammary carcinoma (alanine aminotransferase/arginase = 0.572 ± 0.278) and high arginase activity in hepatitis (alanine aminotransferase/arginase = 12.226 ± 1.822).

Presence of a partial urea cycle in the leech, Poecilobdella granulosa.

Ornithine carbamoyltransferase (OCT) and arginase, but not arginine synthetase (AS), were detected in the body wall and gut tissues of the leech. The activities of these enzymes were not altered by starvation. The high activity of arginase in body wall is probably due to the association of the latter with botryoidal tissue. Hirudineans, which evolved from oligochaete ancestors, appear to have lost the citrulline-arginine segment of the urea cycle due to their ammonotelic mode of nitrogen excretion.

Prostaglandin E2 Production During Hepatic Regeneration Downregulates Kupffer Cell IL-6 Production

The liver possesses the remarkable ability to regenerate to its original size after a 70% partial hepatectomy. There has been little effort to characterize the Kupffer cells' role in this unique mammalian reparative physiologic phenomenon. The capacity of rat Kupffer cells (KC) isolated at specific intervals after partial hepatectomy to produce interleukin-6 (IL-6) and prostaglandin E2 (PGE2) in response to endotoxin was evaluated in standard RPMI-1640 (1200 microM L-arginine) and arginine-depleted RPMI-1640 (10 microM L-arginine) media. Regenerating liver KC 48 to 120 hours after partial hepatectomy responded to endotoxin stimulation with a significantly greater (p less than 0.05) production of IL-6 in standard RPMI-1640. Because Kupffer cells function in an environment where high arginase activity results in negligible L-arginine levels, the 10 microM L-arginine RPMI-1640 was used to simulate the true hepatic microenvironment. Production of IL-6 by regenerating liver KC was further increased (p less than 0.05) by placing these same KC in 10 microM L-arginine RPMI-1640 tissue culture media. During the same period, regenerating liver KC produced significantly (p less than 0.01) more PGE2 than sham-operated KC in both standard and low-arginine media. When the cyclo-oxygenase inhibitor indomethacin (1 x 10(-5) M) was added to cultures, the PGE2 production was inhibited, and IL-6 production was upregulated (p less than 0.05) in arginine-depleted cultures. The authors conclude that during hepatic regeneration KC IL-6 production is elevated but controlled in an autoregulatory fashion by KC PGE2 production.

Kupffer cell autoregulation of IL-1 production by PGE 2 during hepatic regeneration

The mammalian liver possesses the ability to regenerate to its original size after a 70% partial hepatectomy (PHx). The capacity of rat Kupffer cells (KC) isolated at specific intervals following PHx to produce interleukin-1 (IL-1) and prostaglandin E 2 (PGE 2) in response to endotoxin (LPS) was evaluated in standard RPMI-1640 (1200 μ M l-arginine) and arginine-depleted RPMI-1640 (10 μ M l-arginine) media. Regenerating liver KC 48–120 hr following PHx responded to LPS with a significantly greater ( p < 0.05) production of IL-1 in standard RPMI-1640. When 10 μ M l-arginine RPMI-1640 was used to simulate the high arginase activity low l-arginine levels of the hepatic microenvironment, regenerating liver KC production of IL-1 was further increased ( p < 0.05). During the same time period, regenerating liver KC also produced significantly ( p < 0.01) more PGE 2 than sham KC in both high and low arginine media. When the cyclooxygenase inhibitor indomethacin (10 μ M) was added to low arginine cultures, the PGE 2 production was inhibited, and IL-1 production was upregulated ( p < 0.05). We conclude that during hepatic regeneration KC IL-1 production is elevated but controlled in an autoregulatory fashion by KC PGE 2 production.

Nitrogenous waste excretion and accumulation of urea and ammonia inChalcalburnus tarichi (Cyprinidae), endemic to the extremely alkaline Lake Van (Eastern Turkey)

The endemic, anadromous cyprinidChalcalburnus tarichi is the only fish species known to occur in alkaline Lake Van (Eastern Anatolia, Turkey). EightC. tarichi were maintained individually in Lake Van water (17 - 19°C; pH 9.8; 153 mEq·I(-1) total alkalinity; 22‰ total salinity) and tank water samples analyzed for 24 h in 2 to 4 h intervals. At zero time, < 1µM ammonia was present and urea was undetectable in the tank water; at 24 h, total ammonia and urea made up 114±32 and 35±25µM, respectively. Over the experimental period, ammonia-N and urea-N excretion averaged 1041±494 and 607±169μmoles·kg(-1) fish·h(-1), respectively. The extent of urea excretion was highly variable between specimens. Uric acid excretion was not detectable.Urea was present at high concentrations in all tissues and plasma (25 - 35μmoles·g(-1)·ml(-1)) of freshly caughtC. tarichi; total ammonia content of the tissues was by a factor of 1.9 (liver) to 3.0 (brain) lower. High arginase activity (2.4±0.2 U·min(-1)·g(-1)) was detected in the liver ofC. tarichi but ornithine carbamoylphosphate transferase, a key enzyme of the ornithine-urea-cycle, was absent. Ureagenesis is likely through degradation of arginine and/or uricolysis. High glutamine synthetase activity (11±0.6 U·min(-1)·g(-1)) and low ammonia content in brain suggest that, like other teleosts,C. tarichi has an efficient ammonia detoxification in the brain, but in no other tissue.Nitrogenous waste excretion at alkaline pH is discussed. The ability ofC. tarichi to excrete high levels of ammonia at extremely alkaline pH is unique among teleosts studied so far. The mechanism of ammonia excretion under Lake Van conditions remains to be elucidated.

Enhanced phagocytosis of rat alveolar macrophages by intravenous infusion of an arginine-enriched solution.

Phagocytosis of rat alveolar macrophages (AM) was enhanced by the infusion of arginine-rich solution for 7 days. The enhancement of phagocytosis by arginine-rich solution was due to not the difference in the distribution of AM subpopulations (I to IV) but the difference in phagocytic activity of AM in fraction IV. In the process of phagocytosis, there were no significant differences in the stages of migration, attachment, and digestion between control and arginine-rich solutions, although AM from fraction IV of rats infused with arginine-rich solution showed significantly higher ingestion of opsonized sheep red blood cells (SRBC) compared to that of control group. Furthermore, the production of macrophage-activating factor (MAF) from rat splenocytes was higher in arginine-rich group than that of control group. AM from fraction IV of rats fed a stock diet had a higher arginase activity and showed a significant increase of phagocytosis following in vitro incubation with L-arginine (25 and 50 mM) for 24 h. From these results, the enhanced phagocytosis of AM by arginine-rich solution may be due to the increased phagocytosis of AM from fraction IV, in which the higher sensitivity of AM from fraction IV to arginine and the higher production of MAF from splenocytes following the infusion of arginine-rich solution participate.

Enzymes of N-methylputrescine biosynthesis in relation to hyoscyamine formation in transformed root cultures of Datura stramonium and Atropa belladonna

The activities of enzymes related to the biosynthesis of N-methylputrescine, a precursor of the alkaloid hyoscyamine, have been measured in root cultures of Datura stramonium L. and Atropa belladonna L. transformed with Agrobacterium rhizogenes. Ornithine δ-Nmethyltransferase and δ-N-methylornithine decafboxylase were undetectable, indicating that δ-N-methylornithine is an unlikely intermediate in the formation of N-methylputrescine. The activity of putrescine-N-methyltransferase (EC 2.1.1.53) was comparable to, or greater than, that of arginine decarboxylase (EC 4.1.1.19) or ornithine decarboxylase (EC 4.1.1.17). Radiolabel from DL-[5-(14)C]ornithine, L-[U-(14)C]arginine, [U-(14)C]agmaine and [1,4-(14)C]putrescine was incorporated into hyosyamine by Datura cultures. Hyoscyamine production by Datura cultures was substantially inhibited by the arginine-decarboxylase inhibitor, DL-α-difluoromethylarginine, but not by the corresponding ornithine-decarboxylase inhibitor, DL-α-difluoromethylornithine. Together with the demonstration that label was incorporated from [U-(14)C]agmatine, this indicates clearly that arginine is metabolised to hyoscyamine at least in part via decarboxylation to agmatine, even though a high activity of arginase (EC 3.5.3.1) was measurable under optimal conditions. The effect of unlabelled putrescine in diminishing the incorporation into hyoscyamine of label from DL-[ 5-(14)C] ornithine and L-[U-(14)C] arginine does not lend support to the theory that ornithine is metabolised via a bound, asymmetric putrescine intermediate.

Temporal expression of different pathways of 1-arginine metabolism in healing wounds.

Arginine can be metabolized by inflammatory cells through at least two pathways. One is an oxidative l-arginine deiminase (OAD) that results in the formation of citrulline and reactive nitrogen intermediates. The other is arginase, which determines the production of ornithine and urea. The temporal expression of these pathways in an experimental wound model (s.c. implanted polyvinyl alcohol sponges in the rat) was investigated by examining the concentrations of amino acids and of nitrite in fluids obtained from the sponges 6 h to 15 day after implantation. These analyses revealed two distinct periods during which the arginine concentration in the fluids was markedly below plasma levels. During the early period (less than 3 days after sponge implantation) wound fluid contained more citrulline and nitrite than at any other time, suggesting OAD activity. In contrast, ornithine accumulated in the fluids during the late decrease in arginine concentration that extended beyond day 3, during which time the wound fluid also contained a high arginase activity. This time-dependent expression of different pathways of arginine metabolism in wounds was confirmed in sponge cultures containing [guanido-14C]-l-arginine. Cells contained in sponges harvested less than 48 h after implantation metabolized labeled arginine mainly to labeled citrulline, whereas labeled urea was produced during culture of sponges harvested after this time. The low arginine content of wound fluid did not appear to be rate limiting for the expression of OAD in late sponges because no OAD activity was evidenced when 4 mM arginine was added to the cultures. These results indicate that the OAD pathway is expressed in this model predominantly during the early, polymorphonuclear leukocyte-predominant, phase of repair. At this time, the reactive nitrogen intermediates resulting from the metabolism of arginine may mediate some of the events characteristic of early inflammation, including microbiostasis, vasodilation, and inhibition/reversal of platelet aggregation. In turn, the late suppression of this pathway and the catabolism of arginine through arginase may promote macrophage function within wounds.

Rat Liver Arginase Suppresses Mixed Lymphocyte Reaction

An inhibitory factor to mixed lymphocyte reaction (MLR) was purified from the supernatant of rat liver homogenate by procedures including chloroform treatment, ammonium sulfate precipitation, ion-exchange column chromatography, and gel filtration. The molecular weight of the purified inhibitor was 34,000 on SDS-PAGE. We determined the amino acid sequence of the N-terminal region of the purified inhibitor to be Glu-Glu-Pro-Trp-Met-Ser-Met-Ser-Ser-Lys-Pro-Lys-Pro-Ile-Glu-. This sequence shows a high homology to a rat arginase, the amino acid sequence of which was predicted from the nucleic acid sequence of cloned rat arginase cDNA. The amino acid sequence of the purified arginase is 6 amino acid residues longer than the predicted one. The purified MLR inhibitor showed a high arginase activity. The inhibition mechanism was studied and it was discovered that L-arginine was depleted in the culture medium, and that the supply of L-arginine to the cell culture caused recovery of the incorporation of tritium thymidine. Here we present evidence that the MLR inhibitor from rat liver homogenate is the liver arginase. It is noteworthy that immune response may be controlled by a liver factor.

Distribution of arginase and other ornithine cycle enzymes in the gut of the earthworm Lumbricus terrestris L., and some physiological and comparative implications

Abstract 1. 1. Guts of fresh and dehydrated-starved L. terrestris were compared as to tissue and anterior-posterior distribution of arginase, OCT (ornithine carbamoyl phosphate transferase) and AS (arginosuccinase). 2. 2. In fresh worms the anterior two thirds of the midgut was practically devoid of arginase activity, while in starved worms this region exhibited a high arginase activity. Both fresh and starved worms had high arginase activity in the posterior part of the midgut and in the hindgut, and this arginase activity did not increase during starvation. The distribution of AS and OCT was relatively uniform along the gut regardless of state of the worm. 3. 3. The main site of the constant posterior arginase activity was the intestinal epithelium, so part of the posterior midgut epithelium may possibly carry out both ammonia (Prento P. (1989) Comp. Biochem. Physiol. B., in press) and urea production. OCT and AS were always present in both chloragog tissue and epithelium. 4. 4. Starved worms had about four times higher arginase, AS and OCT activities than in fresh worms. Most of the arginase activity (about 70%) was in the chloragog tissue, while the remaining activity was in the intestinal epithelium. This distribution supports Tillinghast (Tillinghast E. K. (1987) J. exp. Zool166, 295–300; and (1986) Comp. Biochem. Physiol.24B 621–623.) as to the excretory route for urea. About 66% of the gut OCT and AS activities were found in the chloragog tissue. 5. 5. The distribution of arginase suggests that both for the intestinal epithelium and for the chloragog tissue high external ammonia levels induce arginase synthesis. The distribution of OCT and AS suggest that arginine synthesis is a property of both the chloragog tissue and the intestinal epithelium.

Arginine metabolism in wounds.

Arginine metabolism in wounds was investigated in the rat in 1) lambda-carrageenan-wounded skeletal muscle, 2) Schilling chambers, and 3) subcutaneous polyvinyl alcohol sponges. All showed decreased arginine and elevated ornithine contents and high arginase activity. Arginase could be brought to the wound by macrophages, which were found to contain arginase activity. However, arginase was expressed by macrophages only after cell lysis and no arginase was released by viable macrophages in vitro. Thus the extracellular arginase of wounds may derive from dead macrophages within the injured tissue. Wound and peritoneal macrophages exhibited arginase deiminase activity as demonstrated by the conversion of [guanido-14C]arginine to radiolabeled citrulline during culture, the inhibition of this reaction by formamidinium acetate, and the lack of prokaryotic contamination of the cultures. These findings and the known metabolic fates of the products of arginase and arginine deiminase in the cellular populations of the wound suggest the possibility of cooperativity among cells for the production of substrates for collagen synthesis.

Cloning and expression in [formula omitted] of cDNA for arginase of rat liver

A cDNA expression library constructed in a plasmid pUC8 from poly(A) + RNA of rat liver was screened immunologically, using an antibody against arginase of rat liver. A cDNA clone was isolated and identified by hybrid-selected translation. The clone contained an insert approximately 1.35 kilobase pairs in length. In the bacterial clone, we detected a specific protein of M r = about 43000 that is slightly larger than the purified arginase ( M r = about 40000) and a high activity of arginase was expressed. The arginase mRNA species of about 1600 bases long was detected in the liver, but not in the small intestine, kidney, spleen and heart of the rats.

Assaying Ornithine and Arginine Decarboxylases in Some Plant Species

A release of (14)CO(2) not related to ornithine decarboxylase activity was found in crude leaf extracts from Lycopersicon esculentum, Avena sativa, and especially from the pyrrolizidine alkaloid-bearing Heliotropium angiospermum when incubated with [1-(14)C]- or [U-(14)C]ornithine. The total (14)CO(2) produced was about 5- to 100-fold higher than that due to ornithine decarboxylase activities calculated from labeled putrescine (Put) found by thin-layer electrophoresis in the incubation mixtures. Partial purification with (NH(4))(2)SO(4) did not eliminate completely the interfering decarboxylation. When incubated with labeled arginine, a very significant (14)CO(2) release not related to arginine decarboxylase activity was observed only in extracts from H. angiospermum leaves, especially in Tris.HCl buffer. Under the assay conditions, these extracts exhibited oxidative degradation of added Put and agmatine (Agm) and also revealed a high arginase activity. Amino-guanidine at 0.1 to 0.2 millimolar prevented Put degradation and greatly decreased oxidative degradation of Agm; ornithine at 15 to 20 millimolar significantly inhibited arginase activity. A verification of the reliability of the standard (14)CO(2)-based method by assessing labeled Put and/or Agm-formed in the presence of added aminoguanidine and/or ornithine when needed-is recommended especially when crude or semicrude plant extracts are assayed.When based on Put and/or Agm formed at 1.0 to 2.5 millimolar of substrate, the activities of ornithine decarboxylase and arginine decarboxylase in the youngest leaves of the tested species ranged between 1.1 and 3.6 and 1 and 1600 nanomoles per hour per gram fresh weight, respectively. The enzyme activities are discussed in relation to the biosynthesis of pyrrolizidine alkaloids.

Arginase activity in the silkworm,Bombyx mori: developmental profiles, tissue distribution and physiological role

Arginase activity was studied in the silk-worm,Bombyx mori. 1. The specific activity remained low from the larval to mid-pupal stage in both sexes. In males, it then increased markedly in the late-pupal stage, reached a maximum in young adults, and then gradually decreased with age, whereas in females it remained almost constant throughout development and ageing (Fig. 1). 2. Of all organs of both sexes, the vesicula seminalis of adult males had the highest arginase activity, the activity in this organ amounting to 95% of the total activity in adult males. The specific arginase activity in this organ was at least 50 times those in other organs. The enzyme activity in the vesicula seminalis increased very greatly during metamorphosis to adults (Tables 1, 2, 3). 3. When the vesicula seminalis was incubated withl-[14C(U)]-ornithine, large amounts of radio-activity were found in the metabolites proline and glutamate, suggesting the conversion of ornithine, produced by arginase, to proline (Fig. 2, Table 4). 4. Proline and succinate were effective substrates for the respiration of silkworm spermatozoa, whereas glucose, α-glycerophosphate and pyruvate were not used.

Activities of glutamine synthetase, glutaminase and arginase in kainic acid lesioned rat brain corpus striatum

Intrastriatal kainic acid (2 μg/μl) administration gave rise to significant increase in activities of glutamine synthetase and arginase along with a significant decrease in the activity of glutaminase in the lesioned striatal tissue 7 days after the administration of kainic acid. The increase in the activity of glutamine synthetase was attributed to the gliosis occurring in such lesions. The decrease in the activity of glutaminase was thought to be due to the loss of GABAergic neurons. The increase in arginase activity might be occurring in glial cells or in nerve endings. Although the earlier results indicated a low specific activity of arginase in glial cells, the observed increase in its activity might be partly due to its increase in proliferating glial cells, liberating ornithine for the formation of polyamines. However, it was also thought that a substantial increase may be occurring in the arginase present in the intact glutamatergic (corticostriate pathway) nerve endings, since it was earlier found that the synaptosomes of the rat brain had appreciably high activity of arginase. These results were discussed in relation to the probable roles of arginine and glutamine as the precursors for neurotransmitter pools of glutamate in striatum.