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PubMed1992

Regulation of aminopeptidase-N (CD13) and Fc epsilon RIIb (CD23) expression by IL-4 depends on the stage of maturation of monocytes/macrophages.

IL-4 has multiple biologic activities and it has been shown to have effects on B and T lymphocytes, mast cells, NK cells, and monocytes. We studied the influence of IL-4 on the expression of cell membrane determinants, in particular aminopeptidase-N (CD13) and Fc epsilon RIIb (CD23), on human peripheral blood monocytes. We compared the response of monocytes with the response of human alveolar macrophages and monocytic cell lines (U937 and THP1), as mature and more immature representatives of the mononuclear phagocyte system, respectively. A dose-dependent increase of the expression of CD13 Ag was observed when monocytes were cultured with IL-4. Kinetic analyses revealed that this induction was maximal after 2 to 3 days of culture and resembled the kinetics of IL-4-induced expression of Fc epsilon RIIb on monocytes. This IL-4-induced increase was absent when monocytes were cultured with IL-4 and an anti-IL-4 antiserum. Concomitantly, an IL-4-induced increase in leucine-aminopeptidase activity could be observed. Northern blot analysis showed that incubation of monocytes with IL-4 induced a marked increase in CD13 mRNA. Alveolar macrophages also exhibited an increase in CD13 Ag expression when exposed to IL-4. Surprisingly, IL-4 was unable to induce expression of Fc epsilon RIIb on alveolar macrophages. U937 and THP1 cells did not show an induction of CD13 Ag when cultured in the presence of IL-4. However, IL-4 did induce the expression of Fc epsilon RIIb on both cell lines, suggesting the presence of functional IL-4R. Our data demonstrate that IL-4 increases the expression of CD13 Ag on monocytes. This IL-4-induced increase can also be observed in more mature monocytic cells such as alveolar macrophages, but is absent in immature cells such as U937 or THP1 cells. This is functionally accompanied by an increase in leucine-aminopeptidase activity and may be part of the general activation of monocytes/macrophages by IL-4. In conclusion, the data suggest that IL-4 responsiveness, in particular the induction of CD13 Ag and Fc epsilon RIIb expression, may be dependent on the stage of maturation of monocytes/macrophages.

Aminopeptidases↗

PubMed1998

High level of resistance to proteinase inhibitors may be conferred by proteolytic cleavage in beetle larvae.

Incorporation of genes encoding proteinase inhibitors into oilseed rape genome could confer resistance to Coleoptera, which are the major pests on rape in Europe. A detailed study of the digestive proteinase of a model cruciferous-feeding Coleoptera, Phaedon cochleariae, showed that this insect relies on a complex proteolytic system including serine, cysteine, aspartyl proteinases, and leucine aminopeptidases. The inhibition of general and specific activities by a range of proteinase inhibitors in vitro suggested that oryzacystatin I (OCI) and Bowman-Birk inhibitor (BBI) would have adverse effects when ingested by the larvae. However, the growth and the feeding of larvae reared on oilseed rape leaf discs treated with a high dose of OCI and/or BBI were not affected. Moreover, the levels and patterns of proteolytic activities were not modified in these larvae. The study of the interactions between P. cochleariae larval proteinases and OCI and BBI revealed that both inhibitors were rapidly cleaved by serine proteinases in association with leucine aminopeptidases, and consequently lost their inhibitory capacity. This mechanism of resistance is very efficient, and may be widespread among Coleoptera. The major implications for insect control using proteinase inhibitor-based strategies are discussed.

Animals↗

PubMedDate not supplied

Effects of malnutrition on the digestive enzymes of the large bowel of young rhesus monkeys.

The aim of the present study was to investigate the effect of mild-to-moderate protein-energy malnutrition (PEM) and rehabilitation on the digestive enzymes of the large bowel in young rhesus monkeys. The presence of these enzymes has already been reported in the large bowel by many authors. The activities of the digestive enzymes, i.e. lactase, sucrase, maltase, trehalase, glucoamylase, leucine aminopeptidase, alkaline phosphatase and gamma-glutamyl transpeptidase, from different parts of the large bowel were determined in 6 controls, 6 PEM and 6 rehabilitated young rhesus monkeys. These monkeys had been used to study the effect of malnutrition on the small intestine and the results have already been published. There was a significant decrease in the sucrase in the ascending colon (p < 0.05); maltase in all the parts of the large bowel (p < 0.05); and glucoamylase activities (p < 0.05) in the caecum segment of the large bowel in the PEM group. The activity of other enzymes, i.e. lactase, trehalase, alkaline phosphatase, gamma-glutamyl transpeptidase and leucine aminopeptidase, was unaffected in the PEM group. The changes in the enzyme activities recovered on rehabilitation of 21 weeks. The result of this study suggest that even mild-to-moderate malnutrition affects the enzyme activity of the large bowel, which recovers on rehabilitation.

Animals↗

PubMed2007

Ethanol-induced oxidative stress suppresses generation of peptides for antigen presentation by hepatoma cells.

UNLABELLED: Processing of peptides for antigen presentation is catalyzed by antigen-trimming enzymes, including the proteasome and leucine aminopeptidase. Oxidative stress suppresses proteasome function. We hypothesized that in liver cells, processing of antigenic peptides is altered by ethanol metabolism. To address this issue, soluble extracts of ethanol-metabolizing VL-17A cells treated with 100 mM ethanol or left untreated were incubated with C-extended or N-extended 18-27 HBV core peptides. Peptide cleavage was measured by recovery after HPLC. Ethanol exposure to VL-17A cells increased CYP2E1 and decreased proteasome peptidase activities. The latter effect was prevented by treatment of cells with inhibitors, 4-methylpyrazole and diallyl sulfide. Ethanol treatment of VL-17A cells also reduced the activity of leucine aminopeptidase (LAP). Consequently, cleavage of both C-extended and N-extended peptides by cytosolic extracts was suppressed by pretreatment of cells with ethanol. Treatment of cells with interferon gamma, which enhances proteasome activity, did not reverse the effects of ethanol. Ethanol exerted similar effects on WIFB cells, indicating that its effects are not unique to one cell type. CONCLUSION: Ethanol metabolism suppresses activities of antigen-trimming enzymes, thereby decreasing the cleavage of C-extended and N-extended peptides. This defect may potentially result in decreased MHC class I-restricted antigen presentation on virally infected liver cells.

Antigen Presentation↗

PubMed1978

Effect of bile acids and pH on the release of enteropeptidase in man.

Bile acids increase the release of human enteropeptidase as well as other brush-border enzymes (alkaline phosphatase, leucine aminopeptidase) from duodenal mucosa, as had been shown earlier in experimental animals. The action of bile acids is independent of their known enhancing effect on enteropeptidase activity. The pH of duodenal juice is an important, hitherto unrecognized, factor in the release mechanism of brush-border enzymes. All of the above enzymes tested were released to a markedly greater extent at pH 8.2 than 6.3, regardless of the presence or absence of bile acid. Contrary to some results obtained with animal tissue, by other investigators, our experiments with human duodenal mucosa indicate that enteropeptidase, under all conditions tested, is released at a rate considerably greater than that for alkaline phosphatase or leucine aminopeptidase. The looser association of enteropeptidase with cellular components relative to that of other brush-border enzymes, as indicated by our observations, may be related to the unique function of enteropeptidase as the trigger enzyme of protein digestion.

Alkaline Phosphatase↗

PubMed1980

[Subchronic toxicity of gamma-Falisan-Universal dry dressing agent to rats].

Doses of 50 mg/kg, 100 mg/kg, and 400 mg/kg of Gamma-Falisan-Universal dry dressing agent (active ingredients including 20 per cent of Lindan and 2.5 per cent of phenyl-mercury acetate) were administered in agar suspension by stomach intubation to rats over 13 weeks, with five applications weekly. The following changes were produced: retardation in body weight, lymphopenia and leucopenia, rise of segment-nuclear neutrophils in peripheral blood, decrease of haematocrit and haemoglobin, as well as rise in activities of leucine aminopeptidase and serum glutamate oxalo-acetate transaminase. The males proved to be more sensitive in the context of their haematological parameters, while the females displayed higher sensitivity in terms of clinico-chemical values. Absolute weight increases were recorded from kidneys and liver of both males and females and from the adrenal gland of females, while weight loss was recorded from the pituitary gland of males. Changes of the same kind were expressed even more strongly, in the context of relative weights of organs. Histopathological changes were recorded from liver, kidneys, and adrenal gland of either sex, and they were histometrically confirmed. Retardation in body weight, rise in activity of leucine aminopeptidase, and weight changes of various organs were significant up to first dosage group. Analogous findings were obtained with regard to microscopic changes in kidneys. Hence, no-effect levels did not occur at all throughout the experiment.

Adrenal Cortex↗

PubMedDate not supplied

The enzymes of the hepatobiliary tract: a biochemical and clinical comparison.

The "biliary tract" enzymes (leucine aminopeptidase, gamma-glutamyltranspeptidase and 5'-nucleotidase) in serum reflect to varying degrees, obstruction, proliferation, inflammation and neoplasia involving the hepatobiliary duct system. Their use is directed towards two purposes: (1) as non-electrophoretic assays to evaluate the source of an elevated non-specific alkaline phosphatase and (2) to offer greater sensitivity and specificity for space-occuping lesions in the liver. In appropriate clinical states, any of the three enzymes offer these advantages and there is little to chose among them. Selection of the assay to use in the clinical laboratory then becomes based on non-clinical factors, i.e., technical ease, apparent substrate specifities, etc. With these additional factors and despite some shortcomings, our selection is leucine aminopeptidase.

Alkaline Phosphatase↗

PubMed1975

Circadian rhythms in digestive enzymes in the small intestine of rats. I. Patterns of the rhythms in various regions of the small intestine.

The activities of the digestive enzymes, maltase [EC 3.2.1.20], sucrase [EC 3.2.1.26], trehalase [EC 3.2.1.28], Leucine aminopeptidase [EC 3.4.11.1], and alkaline phosphatase [EC 3.1.3.1] were measured in various regions of the small intestine of rats. The activities of all these enzymes were much higher in the jejunum than in the ileum, and in the distal regions of the ileum no sucrase, trehalase or alkaline phosphatase activity was detected. In the jejunum, the activities of all the enzymes tested exhibited clear circadian variations with the highest activity at 0000-0400 h and the lowest at 1200 h when the rats were fed ad libitum. In the ileum, maltase and sucrase also exhibited circadian variations, but the amplitude of the rhythm was smaller than that in the jejenum. Trehalase and alkaline phosphatase did not show any circadian variation in the ileum. Leucine aminopeptidase showed a circadian variation in the ileum with the same amplitude as in the jejunum. The phase of the circadian variations shifted about half a day when the rats were fed in the daytime, but the amplitude of the rhythm did not change.

Alkaline Phosphatase↗

PubMed1993

Chromosomal effects on peptidase activities in Drosophila melanogaster.

The peptidase system in Drosophila melanogaster (dipeptidase-A, -B, and -C and leucine aminopeptidases G and P) was used as a model to study the effects of modifier genes on activity of enzymes with similar functions. A screen of X, second, and third chromosome substitution isogenic lines revealed the presence of activity modifiers for peptidases on all three chromosomes. Correlation analyses indicated that covariation between some of the peptidase activities is independent of genetic background, while others are associated with variable second chromosomes. Chromosome-specific effects on Km, Vmax, and specific activity of partially purified peptidases were also detected. Moreover, a repeatable technique using anion-exchange column chromatography allowed the characterization of possibly two putative peptidic enzymes, glycyl-L-isoleucine-ase and L-leucyl-L-proline-ase, whose kinetic properties differ from the dipeptidases and the leucine aminopeptidases. These findings confirm the existence of activity modifiers for peptidases, much like other enzymes in Drosophila melanogaster.

Analysis of Variance↗

PubMed1984

Induction of microvillar hydrolase activities by cell density and exogenous differentiation inducers in an established kidney epithelial cell line (LLC-PK1).

Several hydrolase activities characteristic of the apical brush border membrane of renal proximal tubule, leucine aminopeptidase, gamma-glutamyl transpeptidase, alkaline phosphatase, maltase, and trehalase, were identified in cultures of the LLC-PK1 kidney epithelial cell line. A coordinate increase in activities of these enzymes was observed upon development of a confluent cell density and functional membrane polarization. Further large progressive increases in individual hydrolase activities were induced after the addition of compounds known as differentiation inducers. Hexamethylene bisacetamide preferentially induced increased trehalase and maltase activities. Induced trehalase activity exhibited an increased Vmax but a similar Km compared with activity in control extracts. Induction required protein synthesis and was dependent on inducer concentration and exposure time. Treatment of confluent cultures with N,N'-dimethylformamide triggered an induction of maltase, trehalase, alkaline phosphatase, and gamma-glutamyl transpeptidase activities, whereas dimethylsulfoxide induced trehalase and gamma-glutamyl transpeptidase activities. Increased leucine aminopeptidase and maltase activities were observed after addition of the phosphodiesterase inhibitor 1-methyl-3-isobutylxanthine. Induction of trehalase activity by N,N'-dimethylformamide was reversible over a 4-day period after removal of inducer, but effects of hexamethylene bisacetamide were irreversible. These results suggest that the LLC-PK1 cell line reproducibly develops differentiation-specific characteristics under defined conditions in cell culture, which can be individually modulated by chemicals known as inducers of cell differentiation.

Acetamides↗

PubMed1986

[Enzyme histochemistry of the pig placenta. III. Histotopics of enzymes in the uterine epithelium].

Within the uterine glands, the following enzymes were demonstrated by histochemical methods after 30, 58, 80, 100, and 110 d of pregnancy, respectively: beta-N-acetyl-hexosaminidase, beta-galactosidase, beta-glucuronidase, alpha-mannosidase, acid phosphatase, alkaline phosphatase, esterases, cytochrome oxidase, 5-nucleotidase, leucine aminopeptidase, adenosine triphosphatase, diaphorases (NADH, NADPH), glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, succinate dehydrogenase, isocitrate dehydrogenase (NAD, NADP), beta-hydroxybutyrate dehydrogenase, glycero-3-phosphate dehydrogenase, NAD-glycero-3-phosphate dehydrogenase, glutamate dehydrogenase (NAD, NADP), lactate dehydrogenase. The results show that the activities of G-6-PDH, 6-PGDH, and cytochrome oxidase increase within secreting cells during the 2nd half of pregnancy. The activities of the other enzymes remained almost unchanged during the period of investigation. The description of our results distinguishes between gland neck, middle, and distal part of the secretory unit, respectively. In general, the enzyme activities are similar within the middle and distal gland segments, but lower in the epithelia of the neck region. The activity of dehydrogenases was medium to intensive within the middle and distal gland segments, but only low to medium within the neck portion. Of the hydrolases, the acid phosphatase, ATPase, leucine aminopeptidase, and beta-galactosidase demonstrated an intensive activity within activity secreting cells. The enzyme activities of the gland epithelia are compared with these of the uterine surface epithelia and the histochemical results are discussed in context with their significance in histiotrophic nutrition.

Animals↗

PubMed1980

Enzymatic modifications of human fibroblast and leukocyte interferons.

The sensitivity of highly purified human fibroblast interferon and partially purified human leukocyte interferon to several proteolytic and glycolytic enzymes was determined with respect to antiviral activity, isoelectric point, molecular weight, and thermal stability. Leucine aminopeptidase altered the distribution of isoelectric points for both interferons but produced little change in molecular weights; this enzyme somewhat reduced the activity of only leukocyte interferon. Treatment of fibroblast interferon with carboxypeptidases A and B did not greatly decrease antiviral activity, but it did slightly reduce the molecular weight of the interferon and substantially altered the distribution of isoelectric point values; similar treatment of leukocyte interferon caused some loss in activity, especially of the 17,000-molecular-weight species. Both interferons were inactivated rapidly by treatment with the endoproteases trypsin, pepsin, bromelain, and subtilisin. Chymotrypsin shifted the isoelectric points of both interferons, but only leukocyte interferon was significantly inactivated. Treatment with neuraminidase and beta-galactosidase changed the isoelectric point distribution but did not affect the activity or thermal stability of either interferon; such a treatment reduced the molecular weight of fibroblast interferon and the size heterogeneity of leukocyte interferon. Treatment with neuraminidase and then leucine aminopeptidase greatly reduced the activity of both interferons, especially leukocyte interferon. The data indicate that biologically active forms of fibroblast and leukocyte interferons can be distinguished by their relative sensitivity to certain proteases.

Carboxypeptidases↗

PubMed1989

Effects of prolactin on conceptus survival and uterine secretory activity in pigs.

Hypoprolactinaemia was induced by bromocriptine (CB154; 100 mg/day) which decreased circulating prolactin by 40% (P less than 0.06), but did not affect conceptus survival at Day 25 when administered on Days 10-16 when compared to saline:ethanol-treated control gilts. Bromocriptine or vehicle was administered to cyclic gilts on Days 10-11, oestradiol valerate was injected on Day 11 and uterine flushings were collected on Day 12. Total recoverable protein and uteroferrin in uterine flushings were not affected by treatment. However, leucine aminopeptidase activity (P less than 0.02) and total recoverable Ca2+, Na+, K+ and Cl- (P less than 0.05) were decreased in uterine flushings of gilts that received bromocriptine, suggesting that hypoprolactinaemia decreased general secretory activity of the endometrial epithelium and modulated ionic changes, respectively, in the uterine environment of pigs. Subcutaneous administration of pig prolactin (1 mg/12 h) increased (P less than 0.001) serum prolactin 4.5-fold. The interaction between hyperprolactinaemia and progesterone, without oestrogen, on components of uterine flushings were determined using gilts that received progesterone (200 mg/day) and prolactin or saline on Days 4-14 after ovariectomy on Day 4. On Day 15, there were no differences (P greater than 0.05) in any of the uterine secretory components measured. Hyperprolactinaemia (1 mg pig prolactin on Days 6-11) enhanced overall uterine secretory response on Day 12 to oestradiol (5 mg) administered on Day 11 compared to gilts that received 1 ml saline on Days 6-11 of the oestrous cycle. Total recoverable protein and leucine aminopeptidase activity were greater (P less than 0.05) for oestradiol-treated gilts, but effects of prolactin were not significant. Total recoverable glucose (P less than 0.01), PGF-2 alpha (P less than 0.02), uteroferrin (P less than 0.01) and specific activity of uteroferrin (P less than 0.001) were increased by prolactin and oestradiol, but not oestradiol alone. Calcium (P less than 0.05), chloride (P less than 0.05) and potassium (P less than 0.01) were increased in response to oestradiol. These results indicate an interaction between oestradiol and prolactin, but not progesterone and prolactin, which enhances secretion of some products of the pig uterine endometrium.

Animals↗

PubMed1983

Intestinal brush border hydrolase topography. Effects of vitamin D-3 and filipin.

Intestinal brush borders were isolated from vitamin D-3-treated and vitamin D-deficient chicks, and protein topography in the paired preparations assessed by the enzymatic release of four marker hydrolases. Exposure of the brush borders to the protease bromelain resulted in soluble levels of alkaline phosphatase, leucine aminopeptidase, maltase, and sucrase activities from preparations of vitamin D-3-treated birds that were 42%, 75%, 64%, and 56%, respectively, of corresponding activities released in preparations from rachitic chicks. Analyses for recovery of enzyme activity revealed that bromelain treatment selectively inactivated 43% of the alkaline phosphatase activity of brush borders obtained from vitamin D-3-replete birds, and preferentially diminished recovered sucrase activity in preparations from vitamin D-deficient chicks. In additional experiments, brush borders isolated from rachitic birds were treated in vitro with the polyene antibiotic filipin or an equivalent volume of vehicle. Subsequent exposure of such preparations to bromelain resulted in little or no differences in levels of marker hydrolase specific activities released from filipin- or vehicle-treated brush borders. However, analyses of membrane-bound specific activities after treatment of brush border preparations with a range of filipin concentrations, revealed a biphasic inhibition of approx. 30% for both maltase and sucrase, relative to vehicle controls, and a smaller effect on alkaline phosphatase and leucine aminopeptidase.

Alkaline Phosphatase↗

PubMed1981

High-molecular-mass alkaline phosphatase in serum and bile: nature and relationship with lipoprotein-X.

Using immunoelectrophoresis and other techniques, we have demonstrated an association between lipoprotein-X and (a) alkaline phosphatase and (b) other enzymes originating from the hepatocyte membrane, namely gamma-glutamyltransferase and leucine aminopeptidase. The high-molecular-mass forms of these enzymes, in both serum and bile, were precipitated by lipoprotein-X antiserum but not by antisera to other plasma proteins. The activity of high-molecular-mass alkaline phosphatase in serum was positively correlated with lipoprotein-X and with lipoprotein-X-associated alkaline phosphatase, both assessed semi-quantitatively. On the other hand, many sera possessed high activities of high-molecular-mass alkaline phosphatase but no detectable lipoprotein-X. Incubation of serum with conjugated bile salts and with synthetic detergents, at concentrations which did not dissociate the high-molecular-mass enzymes, caused parallel alterations in the electrophoretic mobility of serum lipoprotein-X and its associated enzyme activity. Incubation of normal dialyzed hepatic bile with normal, lipoprotein-X-negative serum produced an alteration in electrophoretic mobility of biliary lipoprotein and its associated enzyme activity from anodal to cathodal in agar gel. Digestion with papain had a variable effect on the different enzymes in the complex, without affecting the lipoprotein moiety. Leucine aminopeptidase was removed most readily from the complex to give the low-molecular-mass form present in normal serum; gamma-glutamyltransferase dissociated somewhat less readily, and alkaline phosphatase was completely resistant to dissociation from the complex. These results are discussed in the light of current knowledge, and a hypothesis is proposed for the nature of the high-molecular-mass enzymes in serum and bile.

Alkaline Phosphatase↗

PubMed1992

Genetic and environmental effects on the expression of peptidases and larval viability in Drosophila melanogaster.

The peptidase system in Drosophila melanogaster, consisting of dipeptidase-A, dipeptidase-B, dipeptidase-C and the leucine aminopeptidases, was used as a model to study the adaptive significance of enzyme activity variation. The involvement of the peptidases in osmoregulation has been suggested from the ubiquitous distribution of peptidase activities in nearly all tissues and the high concentration of amino acids and oligopeptides in the hemolymph. Under this hypothesis, larvae counteract increases in environmental osmotic stress by hydrolyzing peptides into amino acids both intra- and extracellularly to increase physiological osmotic concentration. The expression of the peptidases was studied by assaying for peptidase activities in third instar larvae of isogenic lines, which were reared under increasing levels of environmental osmotic stress using either D-mannitol or NaCl. Second and third chromosome substitution isogenic lines were used to assess the relative contribution of regulatory and structural genes in enzyme activity variation. Results indicate that: (1) genetic variation exists for peptidase activities, (2) the effect of osmotic stress is highly variable among peptidases, (3) changes in peptidase activities in response to osmotic stress depend on both genetic background and osmotic effector and (4) peptidase activities are correlated with each other, but these phenotypic correlations depend on genetic background, osmotic effector, and level of osmotic stress. Osmotic concentration in the larval hemolymph is correlated with leucine aminopeptidase activity, but changes in hemolymph osmotic concentration in response to environmental osmotic stress depend on the osmotic effector in the environment. Although these findings suggest that genetic and environmental factors contribute significantly toward the expression of enzymes with similar functions, a relative larval viability study of genotypes that differed significantly in dipeptidase-B (DIP-B) activity revealed that low DIP-B activity did not confer any measurable reduction in larval viability under increasing levels of environmental osmotic stress. These negative results suggest that, either DIP-B does not play a major role in osmoregulation or differential osmoregulation is not related to egg to adult viability in these tests.

Animals↗

PubMed1978

Evaluation of histochemical observations of activity of acid hydrolases obtained with semipermeable membrane techniques: a combined histochemical and biochemical investigation 1. The histochemical investigation.

The reliability of enzyme histochemical observations of activities of acid hydrolases was investigated with a combined histochemical and biochemical study. Specimens of m. soleus, m. plantaris, m. gastrocnemius and diaphragm of normal and of vitamin E deficient rabbits were used. For the histochemical investigation, activity and localization of acid phosphatase, beta-glucuronidase, leucine aminopeptidase and E600 resistant non-specific arylesterase were examined with semipermeable membrane techniques. For the biochemical investigation, activity of acid phosphatase, beta-glucuronidase, cathepsin D, acid maltase and neutral maltase was determined. By means of stastical calculations the enzyme activities demonstrated with histochemical techniques were compared with the enzyme activities determined with biochemical techniques. In the present communication the histochemical findings are reported and discussed. From the histochemical findings it appeared that activity of the acid hydrolases investigated is strongly increased in both a granular and a diffuse pattern in skeletal muscle of vitamin E deficient rabbits. The statistical calculations of the histochemical findings clearly reveal that the increased activity of one acid hydrolase was highly significantly paralleled by an increased activity of a second acid hydrolase. Moreover the probability that the activity of all other histochemically studied acid hydrolases was significantly increased was rather high. The increase in activity of the acid hydrolases studied was the same in muscles with an aerobic or an anaerobic metabolism. Moreover there was no difference in activity and localization of the acid hydrolases in aerobic type I and anaerobic type II fibres. The localization of acid phosphatase and beta-glucuronidase activity muscle fibres mostly coincided. In cases where these enzymes were localized both centrally and in the subsarcolemnal areas of the muscle fibres, the activity of E600 resistant naphtholesterase was usually, and the activity of leucine aminopeptidase was exclusively located in the subsarcolemnal areas. All of the examined acid hydrolases were found to be present in the inflammatory exudate and in the connective tissue.

Acid Phosphatase↗

PubMed1979

Renal adaptation to a low phosphate diet in rats.

The major renal adaptive changes in response to selective dietary phosphate restriction are a marked reduction in urinary excretion of phosphate and an increased urinary excretion of calcium; at the cellular level, there is selective increase in renal cortical brush border membrane phosphate uptake and increase in specific activity of alkaline phosphatase. In the present study we examined whether these functional and biochemical adaptive changes could be blocked by drugs known to inhibit protein synthesis. Administration of actinomycin D or cycloheximide to rats switched from a diet with normal phosphate content (0.7%) to a diet with low (0.07%) phosphate content either completely (actinomycin D) or partially (cycloheximide) prevented the expected decrease in urinary excretion of phosphate and increase in the urinary excretion of calcium. The specific activity of alkaline phosphatase measured in crude membrane fraction (washed 100,000 g pellet) from renal cortical homogenate in animals fed a low phosphate diet and treated with actinomycin D or with cycloheximide was significantly lower than in control animals also on a low phosphate diet receiving placebo; but there were no differences between treated and untreated animals in the activities of two other brush border enzymes, gamma-glutamyltransferase and leucine aminopeptidase. Actinomycin D administered to rats maintained on a normal phosphate diet throughout the course of the experiment caused an increase in the urinary excretion of phosphate on the last (6th) day of the experiment but did not change urinary excretion of calcium. In acute clearance experiments, infusion of actinomycin D to rats adapted to a low phosphate diet did not increase fractional excretion of phosphate. In separate experiments, using the same dietary protocol as above, brush border membrane fraction (vesicles) was prepared from renal cortex of rats sacrificed at the end of the experiment. In this preparation Na(+)-dependent (32)Pi and d-[(3)H]glucose uptake and activities of brush border enzymes membrane were determined. Brush border membrane vesicles prepared from rats fed a low phosphate diet showed significantly higher Na(+)-dependent (32)Pi uptake compared with rats fed a normal phosphate diet. This increase in (32)Pi uptake was completely prevented when rats on a low phosphate diet were simultaneously treated with actinomycin D. These differences were specific for (32)Pi transport as no differences were observed in d-[(3)H]glucose uptake among the three groups. There was a positive correlation (r = 0.82, P < 0.01) between (32)Pi uptake and specific activity of alkaline phosphatase measured in aliquots of the same brush border membranes, whereas no such correlation was observed with two other brush border membrane enzymes gamma-glutamyltransferase and leucine aminopeptidase. These observations show that actinomycin D prevents both the functional and cellular renal adaptive changes induced by a low phosphate diet. Taken together, these observations suggest that renal adaptation to a low phosphate diet could be prevented by inhibition of de novo protein synthesis.

Animals↗