Lipoprotein lipase in human milk: compartmentalization and effect of fasting, insulin, and glucose

The object of this study was to investigate the effect of maternal metabolic state on the activity of lipoprotein lipase (LPL) in human milk. Although the total LPL activity in milk was not significantly affected by up to three cycles of freezing and thawing, the amount of LPL associated with the cream fraction of the milk increased from an average of less than 10% to about 70% after this treatment. The enzyme was relatively stable when the milk was stored on ice, losing activity at a rate of about 1% per hour. At 37 degrees C degradation was more rapid, about 7% per hour. When LPL activity was measured in samples taken at hourly intervals by breast pump, using oxytocin to achieve a complete letdown at each pumping, activity was found to double from the first to the third pumping. Thereafter the activity was stable under fasting conditions. Hyperglycemic and euglycemic, hyperinsulinemic glucose clamp protocols were used to evaluate the effects of glucose and insulin. Both high plasma glucose and high plasma insulin in the presence of normal glucose significantly increased LPL activity within 4 hours. We conclude that, like adipose, tissue LPL, mammary LPL is regulated by plasma insulin.     

Subcellular distribution of protein kinase C isoforms in gastric antrum smooth muscle of STZ-induced diabetic rats.

Contractile responses to carbachol (CCh), protein kinase C (PKC) activity and distribution of PKC isoforms in subcellular fractions isolated from gastric antrum smooth muscle of control and streptozotocin (STZ)-induced diabetic rats were examined. CCh induced concentration-dependent contraction in antrum smooth muscle from controls and diabetics, and this contraction was significantly greater in diabetics than in controls. In diabetics, the PKC activity in the nucleus fraction was significantly decreased by about 63% in the resting condition and that in the cytosol fraction was significantly increased by about 135% after the treatment with 10 microM CCh for 10 min compared to controls. Immunoblot analysis showed that 8 PKC isoforms (-alpha, -beta, -gamma, -delta, -epsilon, -zeta, -iota, -lambda) were expressed in rat antrum smooth muscle. The PKC-beta isoform was significantly decreased by about 47% in the nucleus fraction in the resting condition in diabetics compared to controls. The nucleus, cytosol and membrane fractions of this isoform were decreased in controls after the treatment with 10 microM CCh for 10 min whereas these fractions were unchanged in diabetics. The PKC-epsilon significantly increased by about 219% in the cytosol fraction of diabetics in the resting condition, but the distribution of this isoform was unchanged in controls and diabetics after the treatment with 10 microM CCh for 10 min. Results suggest that the diversity of PKC isoform-specific distribution and translocation may be related to abnormal contractility and intracellular signal transduction through the PKC pathway in diabetics.     

HISTOCHEMICAL LOCALIZATION OF ENZYME ACTIVITIES IN ROOT MERISTEM CELLS

Avers , Charlotte J. (Douglass Coll., Rutgers—The State University, New Brunswick, N. J.) Histochemical localization of enzyme activities in root meristem cells. Amer. Jour. Bot. 48(2): 137–143. Illus. 1961,—Particle counts were made in epidermal cells of the root meristem of 2 grasses after exposure of living seedlings to various substrates involved in dehydrogenation reactions. Hydrolytic enzyme activities also were recorded for 1 of these species. The mean number of particles stained with Janus green B was about 90 for each species, but significantly lower counts were obtained in all the dehydrogenase tests. With lactate, pyruvate, glutamate, citrate, and isocitrate as substrates, Phleum cells showed about 25% of the Janus green count, while Panicum cells were about 33% active. These substrates are known to be oxidized by DPN-linked enzymes. The succinic dehydrogenase counts were about 50% of the Janus green total, and 60–70% particle activity was recorded with hexose-phosphate substrates which are probably oxidized in TPN-mediated reactions. In Phleum, particulate activity occurred in the adenosine triphosphatase and aryl sulfatase tests, but a non-particulate distribution characterized 5-nucleotidase activity. The particle counts in the ATPase tests were not significantly different from the Janus green counts, but the 85% particle activity in the aryl sulfatase tests was significantly lower than the Janus green results. These intracellular distributions were compared with those obtained by various authors using biochemical and histochemical techniques and were found to be in close agreement. It was suggested that the evidence indicated intracellular differentiation of at least one kind of cellular organelle, which in all probability was mitochondria.     

Fibrinolytic activity of prostacyclin and iloprost in patients with peripheral arterial disease

We studied the effects of prostacyclin (PGI2) and its stable analog, iloprost, on blood fibrinolytic activity in 33 patients with peripheral arterial disease. Ten subjects (group A) received three 5-hour infusions of iloprost on three consecutive days. The remaining 23 patients received three different 5-hour infusions (placebo, iloprost 2 ng/kg/min, PGI2 5 ng/kg/min). Tissue plasminogen activator (t-PA), total plasma fibrinolytic activity and euglobulin clot lysis time (ECLT) were determined in patients before and after each infusion, both in freely flowing blood samples and following 10 min venous occlusion. In patients of group A, ECLT at rest was significantly shortened after all three iloprost infusions (on average by about 5-11%). First and third infusions produced also shortening of ECLT after venostasis (by 21 and 32%). Statistically significant rise in t-PA activity (by about 68% on average) accompanied only the first infusion. In patients of the group B iloprost provoked significant fall in ECLT at rest (by about 19% on average) only. PGI2 shortened ECLT both at rest and after venous occlusion (by about 17% and 20% on average, respectively) and led to a rise in t-PA activity after venous occlusion by about 33% on average. Our results indicate that prostacyclin and its stable analog, iloprost, enhance fibrinolytic activity in man by releasing or facilitating the release of tissue plasminogen activator from the vessel wall.     

Effect of dietary vitamin B6 contents on antibody production

When mice were placed on diets extreme deficient in vitamin B6, ovalbumin-dependent antibody productions (IgE, IgG1, IgG2a) were significantly suppressed, and alanine aminotransferase activity in the liver was also significantly decreased. In the case of pyridoxine excess (6 mg% = about ten times standard amount) in a 70% casein diet, ovalbumin-dependent antibody productions were also considerably suppressed. These responses were weaker in a low casein (5%) or normal casein (20%) diet than in a 70% casein diet. The administration of high doses of pyridoxine (6 mg%) resulted in the suppression of hepatic cathepsin B activity. Therefore, we conclude that ovalbumin-dependent antibody productions (IgG1, IgE) were suppressed by pyridoxine excess diet (6 mg%), because hepatic cathepsin B activity was suppressed by the excess pyridoxine in diet.     

The effect of betel nut extract on cell growth and prostaglandin endoperoxide synthase in human epidermoid carcinoma cells

The objective of this study was to find out whether prostaglandin endoperoxide synthase (PHS) involves the action of betel nut extract (BNE) on the growth of oral cancers. Therefore, growth and PHS activity were examined in two human oral carcinoma cell lines (OEC-M1 and KB) and one normal fibroblast cell line (NF) in the presence of increasing BNE concentration. BNE at concentrations above 50 microg/ml significantly inhibited the cell growth of OEC-M1 after 72 h in culture, of KB and NF after 48 h in culture. The IC50 of BNE in OEC-M1, KB and NF at 24 h in culture was about 406, 37.5 and 140 microg/ml respectively. PHS activity in OEC-M1 was significantly increased by low BNE concentrations (50 microg/ml, 114%; 100 microg/ml, 33%; 150 microg/ml, 30%) but significantly reduced at higher BNE concentrations (300 microg/ml, 33%; 500 microg/ml, 61%). The PHS activity in KB was significantly inhibited by BNE and this effect was intensified as concentrations increased (50 microg/ml, 31%; 100 microg/ml, 24%; 150 microg/ml, 43%; 300 microg/ml, 60%; 500 microg/ml, 92%). Similar to that in OEC-M1, the PHS activity in NF was significantly increased at low BNE concentrations (50 microg/ml, 139%; 100 microg/ml, 87%;150 microg/ml, 77%) but reduced at higher concentrations (300 microg/ml, 55%; 500 microg/ml, 72%). The PHS activity in all cell lines was almost completely blocked by indomethacin (5 x 10(-6) M). We conclude that these findings suggest that PHS may be an important biochemical mediator of the effect of BNE on the growth of two human oral carcinoma cell lines.     

Changes in body fat and muscle in manual workers at and after retirement

The changes in body fat and muscle in 73 men retiring from manual work have been measured in a longitudinal anthropometric study. Body fat increased by about 3% and body muscle decreased by about 1% between measurements made just before retirement and again 1 year later. The decline in muscle was even greater in a subgroup of 22 men who reported that their activity was less after retirement: but a subgroup of 11 whose activity was said to have been greater after retirement showed an increase in body muscle. A sub-sample of 26 men were measured on five further annual occasions (Fig. 1). The initial increase in body fat was reversed, and fat measurements fell back significantly to or below the pre-retirement values. Body muscle, however, continued to decline steadily at the initial rate, and the ratio of thigh muscle area to body mass fell significantly in retirement in the group as a whole. The possible contributions of ageing and of changes in energy balance and physical activity to these findings are discussed.     

Enzymatic degradation and partial biosynthetic reconstitution of microsomal and mitochondrial membranes.

Guinea pig liver microsomal and mitochondrial membranes were degraded with phospholipase C and D followed by partial biosynthetic reconstitution. Activities of phosphatidylinositol synthetase in microsomal membranes and NADPH-cytochrome c reductase were almost completely lost after phospholipase C and D treatment; almost complete restoration of the original activity was achieved after biosynthesis of phosphatidylcholine in degraded microsomes, but was not reparable after biosynthesis of cytidinediphosphodiglycerides (CDP-diglycerides). The mitochondrial biosynthesis of polyglycerophosphatides was completely retained after degradation of these membranes with phospholipase C, but after similar treatment with phospholipase D, only about one-quarter of the original activity remained, the relative composition of polyglycerophosphatides being significantly different. The activity of NADPH-cytochrome c reductase of microsomes represented about 76% of the original activity after phospholipase C treatment, but only approximately 1% after treatment with phospholipase D. Although this activity could not be restored with CDP-diglyceride synthesis, it was restored to about 75% of the original activity after the biosynthesis of phosphatidylcholine in these fragments. These and additional experimental findings are discussed in terms of the relation between structural organization of lipids and proteins and enzymatic activities of membrane-bound phospholipid-synthesizing enzymes in microsomal and mitochondrial membranes isolated from guinea pig liver.     

Prolonged ischemia differently affects phospholipase C acting against phosphatidylinositol and phosphatidylinositol 4,5-bisphosphate in brain subsynaptosomal fraction

The effect of 10 min ischemia on the activity of phospholipase C acting against [3H]inositol-phosphatidylinositol (PI) and [3H]inositol-phosphatidylinositol 4,5-bisphosphate (PIP2) in the brain subsynaptosomal fractions was investigated. In the presence of endogenous CaCl2, specific activity of phospholipase C acting on phosphatidylinositol was as follows: synaptic cytosol (SC) greater than synaptic vesicles (SV) greater than synaptic plasma membrane SPM). Brain ischemia activated phospholipase C acting on PI by about 60% and 40% in SV and SPM, respectively. The enzyme of synaptic cytosol was not affected by ischemic insult. Phospholipase C acting against PIP2 in the presence of endogenous calcium expressed the specific activity in the following order: SV greater than SPM greater than SC. After 10 min of brain ischemia, activity of phospholipase C acting on PIP2 was significantly suppressed in all subsynaptosomal fractions by about 50-60%. These results indicate that prolonged ischemia produced activation exclusively of phospholipase C acting against phosphatidylinositol.     

Increased acetylcholinesterase activity in selected regions of rat brain after chronic (−)-Deprenyl administration

(−)-Deprenyl, 0.05, 1.0, 2.0, and 10.0 mg/kg body weight, was administered intraperitonially to Wistar rats for 30 days. The activity of acetylcholinesterase, and monoamine oxidase A and B were assayed in different brain regions. After the experimental period acetyl cholinesterase activity was found to be significantly increased in frontal cortex [P<0.001] and hippocampus [P<0.001] but not in striatum and brainstem at 0.1, 1.0, and 2.0 mg/kg dose, the maximum increase being at 0.1 mg/kg dose. Monoamine oxidase B activity was inhibited by more than 90% at 1.0, 2.0, and 10.0 mg/kg dose while 0.05 and 0.1 dose inhibited only about 55% and 70% respectively. Monoamine oxidase A activity was inhibited to more than 70% at 1.0 mg dose and to more than 90% at 2.0 and 10.0 mg/kg dose. At 0.05 and 0.1 mg/kg dose monoamine oxidase A activity was not significantly altered.     

丝孢菌Monodictys asperospera (Cooke & Massee) Ellis漆酶的分离纯化及其酶学性质

本研究首次发现Monodictyx asperospera(Cooke&Massee)Ellis具有较好的产漆酶能力.粗酶液经硫酸铵盐析、DEAE-纤维素层析及丙烯葡聚糖凝胶S-300层析纯化,纯化倍数为8.1,回收率为5.7%.漆酶分子量约为77kD,最适反应温度为55℃,最适反应pH6.0,以丁香醛连氮为底物时Km为0.163mm0l/L,Vmax为0.194 mmol(L·min),含糖量为18.14%,Cu2+对漆酶有明显抑制作用.     

The Mz variety of the St(a+) phenotype--a variant of glycophorin A exhibiting a deletion

The NeuNAc level of erythrocyte membranes from two related donors exhibiting the Mz variety of St(a+) phenotype within the MNSs blood group system was found to be decreased by about 16%. The quantity of glycophorin A was decreased by about 38%, whereas that of glycophorin B was not significantly different from normal. Mz erythrocyte membranes were also found to contain an abnormal component (molar ratio to glycophorin A about 0.89:1.0) with an apparent molecular mass of about 24,000 Da. Immunoblotting experiments and amino-acid sequence analysis revealed that the novel component (and glycophorin A in one of the donors) carries blood group M activity. Blood group N activity was demonstrable for glycophorin A and glycophorin B from both donors. Amino-acid sequence analysis of chymotryptic, tryptic and cyanogen bromide peptides demonstrated that the novel molecule exhibits the typical structure of a Sta-active molecule. However, since it exhibits blood group M activity, it appears to represent a variant of glycophorin A lacking the residues 27-58 (encoded by exon three of the glycophorin A gene) rather than a glycophorin B-glycophorin A-hybrid molecule of the anti-Lepore type. Since one of the Mz heterozygotes was found to exhibit both M- and N activity on glycophorin A, the Mz gene complex appears to encode a blood group N-active glycophorin A apart from the novel component and a blood group s-active glycophorin B, although the level of glycophorin A in the erythrocyte membranes is decreased by about half.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of heavy metals on common carp white blood cells in vitro

The in vitro effects of cadmium, copper, lead and zinc, and various cadmium compounds (chloride, sulphate and nitrate) on common carp (Cyprinus carpio) lymphocyte viability and phagocyte activity, were evaluated. The percentage of dead lymphocytes was determined after Trypan blue staining, and phagocyte activity was measured by using the nitroblue tetrazolium (NBT) reduction test. Lead was the most toxic to lymphocytes--the maximum mortality exceeded 30%, and was significantly higher at 1 microM of lead, compared to the control. The maximum mortality caused by cadmium was below 10%, but was significantly elevated with 5 microM or more of cadmium. Zinc induced lymphocyte mortality from 10 microM, whilst no effect was observed with copper. The incubation of full blood with the three cadmium compounds (at 5mg/l of cadmium) showed that cadmium nitrate and cadmium sulphate were more toxic (over 35% and 25% mortality, respectively) than cadmium chloride (about 15% mortality). This was confirmed by the results of tests on isolated cells--1mg/l of cadmium as nitrate and sulphate increased lymphocyte mortality compared to the control and cadmium chloride. Phagocytic activity was less sensitive to heavy metals than was lymphocyte viability. It was significantly reduced following exposure to 50 microM and 100 microM cadmium, and 100 microM zinc, but no effects were observed with either lead or copper.     

Corynebacterium glutamicum superoxide dismutase is a manganese-strict non-cambialistic enzyme in vitro

Superoxide dismutase (SOD) of Corynebacterium glutamicum was purified and characterized. The enzyme had a native molecular weight of about 80kDa, whereas a monomer with molecular weight of 24kDa was found on SDS-PAGE suggesting it to be homotetramer. The native SOD activity stained gel revealed a unique cytosolic enzyme. Supplementing growth media with manganese increased the specific activity significantly, while adding iron did not result in significant difference. No growth perturbation was observed with the supplemented media. In vitro metal removal and replacement studies revealed conservation of about 85% of the specific activity by substitution with manganese, while substitution with copper, iron, nickel or zinc did not restore any significant specific activity. Manganese was identified by atomic absorption spectrometer, while no signals corresponding to fixing other metallic elements were detected. Thus, C. glutamicum SOD could be considered a strict (non-cambialistic) manganese superoxide dismutase (MnSOD).     

Light dependency of the cytokinin-induced bud initiation in protonemata of the moss Funaria hygrometrica

The activities of starch synthesizing enzymes were investigated in wheat grains ( Triticum aestivum L. cv. Kolibri) throughout the grain development period. Starch phosphorylase (E.C. 2.4.1.1.) activity was especially high during the early period of grain development, while starch synthase I (ADP glucose α-glucan 4-α-glucosyl-transferase, E.C. 2.4.1.21) had a maximum activity during the later stage of grain filling. The synthetic potential of starch phosphorylase measured in vitro was about 16 times higher than the quantity of starch actually produced. It is therefore suggested that starch phosphorylase is of substantial importance in grain starch synthesis, particularly in the early period of grain growth. The synthetic potential of starch synthase I measured in vitro made up 25 to 50% of the starch production and the synthetic potential of starch synthase II (UDP glucose α-glucan 4α-glucosyl-transferase. E.C. 2.4.1.11) only about 5%.
Reducing light intensity (shading) during the grain filling period depressed grain growth and starch production by about 20%. Starch phosphorylase was not significantly affected by the reduced light intensity if enzyme activity is calculated on unit grain weight and not as activity per grain. Starch synthase I activity, however, was depressed by shading during the later stage of grain development. The depressed starch production found under low light conditions, however, cannot only be explained by an affected starch synthase I activity, but probably was also related to other still unknown factors limiting grain growth under low light conditions. The poor starch production in the shaded plants was not due to an insufficient supply of assimilates.     

Physical Activity Levels and Domains Assessed by Accelerometry in German Adolescents from GINIplus and LISAplus

Background

Physical activity (PA) is a well-known and underused protective factor for numerous health outcomes, and interventions are hampered by lack of objective data. We combined accelerometers with diaries to estimate the contributions to total activity from different domains throughout the day and week in adolescents.

Methods

Accelerometric and diary data from 1403 adolescents (45% male, mean age 15.6 ± 0.5 years) were combined to evaluate daily levels and domains of sedentary, light, and moderate-to-vigorous activity (MVPA) during a typical week. Freedson’s cutoff points were applied to determine levels of activity. Total activity was broken down into school physical education (PE), school outside PE, transportation to school, sport, and other time.

Results

About 2/3 of adolescents’ time was spent sedentary, 1/3 in light activity, and about 5% in MVPA. Boys and girls averaged 46 (SD 22) and 38 (23) minutes MVPA per day. Adolescents were most active during leisure sport, spending about 30% of it in MVPA, followed by PE (about 20%) transport to school (14%) and either school class time or other time (3%). PE provided 5% of total MVPA, while leisure sport provided 16% and transportation to school 8%. School was the most sedentary part of the day with over 75% of time outside PE spent sedentary.

Conclusions

These German adolescents were typical of Europeans in showing low levels of physical activity, with significant contributions from leisure sport, transportation and school PE. Leisure sport was the most active part of the day, and participation did not vary significantly by sex, study center (region of Germany) or BMI. Transportation to school was frequent and thus accounted for a significant fraction of total MVPA. This indicates that even in a population with good access to dedicated sporting activities, frequent active transportation can add significantly to total MVPA.     

Masking of the circadian rhythms of heart rate and core temperature by the rest-activity cycle in man

Heart rate and core temperature are elevated by physical activity and reduced during rest and/or sleep. These masking effects may confound interpretation of rhythm waveforms, particularly in situations where the rest-activity rhythm has a different period from that of the core temperature rhythm. Such desynchronization often occurs temporarily as an individual adjusts to a new work shift or to a new time zone following rapid transmeridian travel, making it difficult to assess the impact of such schedule changes on the circadian system. The present experiments were designed to estimate the magnitude of these masking effects, by monitoring the heart rate, rectal temperature, and nondominant wrist activity (2-min samples) of 12 male subjects during 6 days of normal routine outside the lab and during 6 days of strict bedrest. Subjects also kept sleep, dietary, and exercise logs throughout the study. Average (20-min) waveforms were computed for each subject and each rhythm, at home and in bedrest. In addition, data were partitioned according to self-reported sleep and wake times and were analyzed separately for each state. Average waveform comparisons indicated that about 45% of the range of the circadian heart rate rhythm during normal routine was attributable to the masking effects of activity during wake, which also produced a 16% elevation in mean heart rate during wake and an 11% increase in mean heart rate overall. (Analysis of variance indicated that mean heart rate during sleep at home was not significantly different from the mean during sleep in bedrest.) On average, about 14% of the range of the circadian temperature rhythm during normal routine was attributable to the effects of activity masking. However, the change in range of the temperature rhythm, from home to bedrest, was very variable between subjects (-41% to +13%). This variability was not accounted for by age or by reported frequency of exercise at home. Normal activity during wake increased the mean temperature during wake by an average of 0.16 degrees C and the overall mean by about 0.12 degrees C. (Analysis of variance indicated that mean temperature during sleep at home was not significantly different from the mean during sleep in bedrest.) A 10-hr "night" (lights-off from 2200 to 0800 hr) was provided during bedrest, within which subjects could select their own sleep times. Times of sleep onset and wake onset were not significantly different between home and bedrest.(ABSTRACT TRUNCATED AT 400 WORDS)     

Amelioration of cisplatin-induced nephrotoxicity in rats by tetramethylpyrazine, a major constituent of the Chinese herb Ligusticum wallichi

Nephrotoxicity of the anticancer drug, cisplatin (CP) involves enhanced renal generation of reactive oxygen metabolites and lipid peroxidation caused by decreased levels of antioxidants and antioxidant enzymes. Tetramethylpyrazine (TMP) is known to act as a strong antioxidant. Therefore, in the present work, we aimed at testing the possible protective or palliative effect of TMP on CP nephrotoxicity in rats. TMP was given orally at a dose of 80 mg . kg(- 1) . day(- 1) for 7 days. Some of these rats were given a single intraperitoneal injection of CP (or vehicle) at a dose of 6 mg/kg on Day 6 of treatment. Animals were sacrificed 6 days after CP (or vehicle) treatment, and blood, urine, and kidneys were obtained. Nephrotoxicity was assessed biochemically by measuring creatinine and urea in serum, reduced glutathione (GSH) concentration in renal cortex, by urinalysis, and histopathologically by light microscopy. CP significantly increased the concentration of urea and creatinine (P < 0.05) by about 128% and 170%, respectively; increased urine volume and N-acetyl-beta-D-glucosaminidase (NAG) activity; and significantly decreased osmolality and protein concentrations. CP treatment reduced GSH by about 34% (P < 0.05) and superoxide dismutase (SOD) and total antioxidant activity (TOX) by about 28% and 21%, respectively (P < 0.05). TMP pretreatment significantly mitigated all of these effects. Sections from saline- and TMP-treated rats showed apparently normal proximal tubules. However, kidneys of CP-treated rats had a moderate degree of necrosis. This was markedly reduced when CP was given after pretreatment with TMP. CP cortical concentration was not significantly altered by TMP treatment. The results suggest that TMP ameliorated the histological, physiological, and biochemical indices of nephrotoxicity in rats. Pending further pharmacological and toxicological studies, TMP may potentially be useful as a nephroprotective agent.     

Effect of starvation on lipoprotein lipase activity in the liver of developing rats

Liver lipoprotein lipase activity in neonatal (1- and 5-day-old) rats was 2-3-times than in the liver of adult rats. In mid-suckling (15-day-old) or weaned (30-day-old) animals, it was not significantly different from the low activity detected in adult rats. Starvation resulted in a 3-fold increase of lipoprotein lipase activity in the neonatal liver, but did not affect the activity in the liver of mid-suckling, weaned or adult rats. When isolated livers from both 1- and 5-day-old pups were perfused with heparin, a sharp peak of lipoprotein lipase activity appeared in the perfusate. In fed neonates, the peak area accounted for about 70% of the total (released + non-releasable) activity. In starved neonates, the proportion of heparin-releasable activity increased up to about 90%. These results indicate that neonatal rat liver lipoprotein lipase activity is markedly affected by changes in the nutritional status of the animal, and the effect is restricted to the vascular pool of the enzyme, as was reported in extrahepatic tissues from adult rats.     

Arginase-flotillin interaction brings arginase to red blood cell membrane

Flotillin-1 and arginase are both up-regulated in red blood cell membrane of type 2 diabetic patients. For studying why the soluble arginase can bind to the membrane and whether such binding would modify arginase activity, the arginase1 and related proteins were cloned and expressed. The results showed that flotillin-1 can interact with arginase1, and hence arginase activity was up-regulated by 26.8%. It was estimated that about 61% of arginase1 is bound to the membrane mediated by flotillin-1. The arginase activity in diabetic patients was significantly higher than that of the controls (752.4+/-38.5 U/mg protein vs 486.7+/-28.7 U/mg protein).