The presence of a low molecular weight acid phosphatase in liver tissue that cannot be demonstrated with the histochemical substrate naphthol AS-BI phosphate

Summary Three distinct isoenzymes of acid phosphatase have been separated from extracts of liver tissue of rats by gel filtration. These isoenzymes have molecular weights of 180,000±35,000; 74,000±11,000 and 13,000±2,500. High molecular weight isoenzymes and a low molecular weight isoenzyme of acid phosphatase (molecular weight 13,000±2,100) were also present in extracts of normal human and mouse liver tissue, and of pathologically altered liver tissue of mice in which the activity of acid phosphatase was strongly increased as a result of intraperitoneal injections of dextran solutions. Activity of acid phosphatase was determined with three substrates. The isoenzymes showed different conversion rates for the three substrates. The high molecular weight isoenzymes split the substrates 4-methylumbelliferyl phosphate, p-nitrophenyl phosphate and naphthol AS-BI phosphate. The activity was sensitive to the inhibitors fluoride and L(+)tartrate. In the pathologically altered liver tissue, which had stored dextran, the activity of these isoenzymes was strongly increased. The low molecular weight isoenzyme split 4-methylumbelliferyl phosphate and p-nitrophenyl phosphate but not naphthol AS-BI phosphate. Therefore this isoenzyme cannot be demonstrated with histochemical techniques using the substrate naphthol AS-BI phosphate. In contrast to the activity of the high molecular isoenzymes the activity of the low molecular isoenzyme was not changed in the pathologically altered liver tissue of mice and was not sensitive to the inhibitors fluoride and L(+)tartrate.This study was supported by a grant from the Prinses Beatrix Fonds, s'Gravenhage     

Confocal microscopical analysis of epithelial cell heterogeneity in mouse Peyer's patches

Summary Cyanine dye fluorescence and alkaline phosphatase activities have been compared directly by confocal microscopy in a wide variety of cells present in the follice-associated epithelium of the mouse Peyer's patch to test the hypothesis that antigen-transporting M cells have a low membrane potential. In order to make these comparisons it was first necessary to equilibrate living tissue with the membrane potential sensitive dye DIOC₅(3), fix with glutaraldehyde and then incubate the fixed tissue with naphthol AS-BI phosphate, a substrate which is hydrolysed by alkaline phosphatase present in the luminal membrane of these epithelial cells. Naphthol AS-BI produced by this reaction, is then coupled to Fast Red TR diazonium salt at the site of hydrolysis. Selecting the 488 nm wavelength of the argon laser source then allows one to measure alkaline phosphatase activities as Fast Red absorbance and membrane potentials by DIOC₅(3) fluorescence.Results obtained show a linear correlation between membrane potential and alkaline phosphatase activity. Relative lack of alkaline phosphatase activity, determined in fixed tissue, has been used previously to identify antigen-transporting M cells (Smithet al., 1987). The present work shows that it is now possible to recognize these cells in living tissue by measurement of DIOC₅(3) fluorescence. The possible importance of this finding in providing a way to study cell surface-antigen interactions taking place in living tissue is discussed.     

Kinetic characterization of unspecific alkaline phosphatase at different villus sites of rat jejunum

Summary A quantitative histochemical method to determine the apparent Km and V _max values of rat intestinal unspecific alkaline phosphatase at different sites of the villi is described. Naphthol-As-Bi-phosphate (0.025–1.5 mM) is employed as substrate and Fast Blue B as coupling reagent, and the resulting azo-dye in the brush border membrane has an absorbance maximum at 550 nm. The ratio between the absorbance at 550 and 500 nm is constant as calculated from automatically recorded spectra at different intense dye deposits. Its absorbance is a linear function of incubation time up to 3 min and thickness of the slices up to 10 m both with medium (0.5 mM) and high (1.5 mM) substrate concentrations. Using the histochemical assay under comparable conditions in test tube experiments with homogenates of intestinal mucosa an app. Km of 0.26±0.081 mM (weighted regression analysis) and 0.28–0.084 mM (direct linear plotting) is determined, demonstrating an affinity to the histochemical substrate, which is about 10 times higher than for p-Nitro-phenyl-phosphate with the purified enzyme.The results obtained by scanning the total dye deposits along jejunal villi show considerable differences in enzymatic activity between single villi and an increase from the villus base up to the transition between medium and apical villus third. As well in the apical region as at the villus base saturation curves are obtained by determining the relationship between the absorbance and the substrate concentration under standard conditions (slice thickness 10 m, incubation time 3 min, 37°C, pH 8.3). Calculated by weighted regression analysis and direct linear plotting from the absorbance data of six female rats the medium app. kinetic data ±SD from the jejunal villi read as follows. Apical: Km=0.81±0.438 mM, V _max=3.99±1.217 absorbance units (A) and Km=0.87±0.428 mM, V _max=4.02±1.191 A, respectively. Basal: Km=0.82±0.261 mM, V _max=3.26±0.719 A and Km=0.77±0.184 mM, V _max=3.04±0.518 AU, respectively. As demonstrated by factorial analysis of variance only V _max is influenced by the villus position.Supported by the Deutsche Forschungsgemeinschaft GU 184/1     

Lectin binding in skeletal muscle. Evaluation of alkaline phosphatase conjugated avidin staining procedures

Summary Cryostat sections from rat gracilis muscles were incubated with different biotinylated lectins: Con A (Concanavilin A), WGA (Wheat germ agglutinin), SBA (soybean agglutinin), GS I and GS II (Griffonia simplicifolia agglutinin), LCA (Lens culinaris agglutinin), PNA (peanut agglutinin) and PSA (Pisum sativum agglutinin). The sections were subsequently treated with alkaline phosphatase conjugated avidin. The lectin binding sites were visualized after incubation in substrate media containing: (1) 5-bromo-4-chloro indoxyl phosphate and Nitro Blue tetrazolium or copper sulphate; (2) naphthol AS-MX phosphate or naphthol AS-BI phosphate and various types of diazonium salts; (3) -naphthylphosphate and Fast Blue BB; (4) -glycerophosphate according to the method of Gomori. The results obtained with the alkaline phosphatase methods were compared with those seen with a streptavidin-horseradish peroxidase procedure. Several chromogen protocols for visualizing alkaline phosphatase activity showed differences in the ability to detect lectin binding sites. A sarcoplasmic reaction was evident for Con A, GS II, WGA, LCA, and PSA after incubation in the indoxyl phosphate medium. Sarcoplasmic reaction for GS II was also noticed after incubation with naphthol AS-MX Fast Blue BB and -glycerophosphate. The latter substrate also gave rise to a sarcoplasmic Con A reaction. With the indoxylphosphate tetrazolium salt method some muscle fibres showed a very strong intracellular reaction after incubation with Con A and GS II while the staining intensity was weak in other fibres. The same muscle fibres were stained with PAS. No sarcoplasmic reactions were observed with either naphthol phosphate media or with the diaminobenzidine peroxidase methods. Further, the staining of the muscle fibre periphery, connective tissue, and capillaries was intensified using the indoxyl method. The indoxylphosphate-tetrazolium salt method seems to be suitable for future investigations of lectin binding sites in muscle sections.     

A study of acid phosphatase in mouse kidney using naphthol AS/BI phosphate as a substrate

Summary A kinetic study of mouse kidney acid phosphatase has been performed using an application of the histochemical method ofBurstone (1958a, b). The suitability of the use of naphthol AS/BI phosphate as a substrate for biochemical assays of acid phosphatase has been ascertained. However, the rate of inhibition of the enzyme by sodium molybdate and sodium fluoride suggests that naphthol AS/BI phosphate may represent a substrate for an acid phosphatase different from-glycerophosphatase.     

The increase in activity of acid hydrolases in muscles of rats after subcutaneous administration of dimethyl-para-phenylene diamine. A combined histochemical and biochemical investigation

Summary The increase in activity of acid hydrolases in skeletal muscles of rats after subcutaneous administration of dimethyl-para-phenylene diamine (DPPD) was studied with a combined histochemical and biochemical investigation. In part I the histochemical findings were presented. In this communication the biochemical findings are reported and compared with the histochemical findings.In homogenates of m. biceps femoris, m. gastrocnemius and m. rectus femoris of DPPD-treated rats, the activity of the lysosomal acid hydrolases, cathepsin D, acid maltase, acid phosphatase, and -glucuronidase was increased. This increase in activity was maximal after 7 to 9 days of DPPD treatment and ran parallel to the severity of the pathological changes. Statistical calculations clearly reveal that the increased activity of one acid hydrolase was significantly paralleled by an increased activity of a second acid hydrolase. Moreover these calculations reveal that the biochemical activity findings correlated with the histochemical activity findings. However it was remarkable that in the histochemical study, the estimated increase in acid phosphatase activity was much more than the increase in acid phosphatase activity found biochemically, whilst on the other hand the histochemically estimated increase in -glucuronidase activity corresponded with the biochemical observations. The results of gel filtration techniques have shown that this discrepancy of acid phosphatase activity was caused by different substrate specificity of the different isoenzymes of acid phosphatase and that as a result of the DPPD treatment the isoenzyme pattern had been altered. The elution patterns showed three distinct isoenzymes of acid phosphatase of normal and of DPPD treated rats. These isoenzymes, termed I, II and III, have molecular weights of: 200,000 or more, 83,500–104,500 and 14,500–18,100. Isoenzymes I and II split the substrates 4-methylumbelliferyl phosphate and naphthol AS-BI phosphate and the activity is strongly increased in the muscles of the DPPD treated rats. Isoenzyme III does not split naphthol AS-BI phosphate and the activity is not increased in the muscles of the DPPD treated rats. Considering the fact that it has been shown that the activity of isoenzyme III is high compared with that of the isoenzymes I and II, it is important to realise that by using naphthol AS-BI phosphate not all acid phosphatase can be demonstrated in sections of skeletal muscle.This study was partly supported by a grant from the Prinses Beatrix Fonds, 's Gravenhage, The Netherlands, and was mainly extracted from the Ph. D. thesis of D.E. Israël (1977).     

Quantitative histochemical study of acid phosphatase activity in rat liver using a semipermeable membrane technique

Acid phosphatase activity has been demonstrated in rat liver with the semipermeable membrane technique using naphthol AS-BI phosphate as substrate and hexazotized pararosaniline (HPRA) as simultaneous coupling agent. With this method the final reaction product (FRP) appeared in rat liver as intensely colored red granules in liver parenchymal cells and in Küpffer cells. The absorbance spectrum of the FRP peaks between 510 and 550 nm. A nonspecific reaction product, as has been found in skeletal muscle, did not occur in rat liver. A substrate concentration of 5 mM and a HPRA concentration of 10 mM result in optimum localization and activity. We concluded from the results with different enzyme inhibitors that lysosomal acid phosphatase was demonstrated. The mean absorbance of the FRP increased linearly with incubation time (15-60 min). Furthermore, we found a linear increase of the FRP with increasing section thickness (4-10 micron). When the simultaneous coupling method was replaced by a post-coupling technique, the colored reaction product was diffusely located throughout the cytoplasm. In conclusion, the simultaneous coupling technique in combination with the semipermeable membrane method is a valuable tool for detecting and quantifying lysosomal acid phosphatase activity in rat liver. We demonstrated that acid phosphatase activity is 1.2 times higher periportally than pericentrally in rat liver, and that 24 hr fasting before the experiments did not change the acid phosphatase activity.     

Automated histochemical analysis of cell populations in the intact follicle-associated epithelium of the mouse Peyer's patch

Summary A new technique of quantitative histochemistry has been developed to study the cellular composition of the follicle-associated epithelium of the mouse Peyer's patch. This technique involves applying naphthol AS-BI phosphate to the surface of intact tissue where it is hydrolysed by alkaline phosphatase present in the luminal membrane of the epithelial cells. Naphthol AS-BI produced by this reaction is then coupled to Fast Red TR diazonium salt at the site of hydrolysis. M cells present in the epithelium contain little alkaline phosphatase activity and, therefore, remain white. Treatment with Alcian Blue is finally used to label goblet cells. Subsequent quantitative analysis of alkaline phosphatase-rich cells is carried out by scanning microdensitometry. Using this technique it is possible to detect two populations of alkaline phosphatase-containing cells in mice reared in a normal animal house environment.These results are discussed in relation to possible interactions taking place between enteric antigens and the gut-associated lymphoid tissue which could reduce the ability of follicle-associated enterocytes to express alkaline phosphatase.     

Evaluation of histochemical observations of activity of acid hydrolases obtained with semipermeable membrane techniques. 3. The substrate specificity of isoenzymes of acid phosphatase in m.gastrocnemius of rabbits.

Three distinct isoenzymes of acid phosphatase have been separated from extracts of m.gastrocnemius of normal and of vitamin E deficient rabbits by gel filtration and polyacrylamide gel electrophoresis. These isoenzymes, termed I, II and III, have molecular weights of: 110,000--130,000, 60,000--78,000 and 12,500--14,500. Isoenzymes I and II split the substrates 4-methylumbelliferyl phosphate and naphthol AS-BI phosphate and the activity is strongly increased in the muscles of vitamin E deficient rabbits. Isoenzyme III splits only 4-methylumbelliferyl phosphate and the activity is not increased in the muscles of vitamin E deficient rabbits. The pH-optimum for isoenzymes I and II is 4.8 and for isoenzyme III 5.5. It has been shown that the histochemical semipermeable membrane technique, using substrate naphthol AS-BI phosphate, is a very reliable technique for demonstrating activity of the isoenzymes I and II in tissue sections. On the other hand, activity of isoenzyme III cannot be demonstrated with this histochemical technique. In pathologically altered muscles, the activity of the isoenzymes I and II is greatly increased whilst the activity of isoenzyme III is not significantly altered.     

Phosphates of the naphthol AS series in the quantitative determination of alkaline and acid phosphatase activities “in situ” studied in polyacrylamide membrane model systems and by cytospectrophotometry

Summary Histochemical media for the demonstration of alkaline and acid phosphatases using phosphates of naphthol AS series as the substrates and various diazonium salts as the couplers were tested in the capability of reflecting various levels of enzyme activities.Polyacrylamide membranes with incorporated enzymes (various concentrations of purified enzymes as well as of sonicated leucocytes, macrophages and of sonicated homogenates of various organs) were used as model systems in which the activity was estimated both with biochemical and with histochemical methods. Parallel experiments were performed in sedimentation chamber preparations of guinea-pig leucocytes and macrophages in which the activity was demonstrated with the same media as in polyacrylamide films. The quantitative measurements were performed in a cytospectrophotometer using the two-wavelength method.Increasing the substrate concentration which in standard histochemical media has been 1/8 mg per ml more azo-dye is produced in the reactions for both phosphatases. If the substrate concentration is higher than 1/2 mg per ml the standard concentration of the diazonium salt (1 mg per ml) becomes insufficient for an effective capturing of the released naphthol AS in the reaction for alkaline phosphatase. Due to a very high inhibitoty effect in the case of most commercially available diazonium salts the increase of their concentration annules the beneficial action of an increased substrate concentration on the azo-dye production. 4-amino-diphenylamine diazonium sulfate has an exceptional position because it was not inhibitory even in the concentration of 4 mg/ml.In the case of acid phosphatase the higher substrate concentration was incompatible with the use of Past Red Violet LB. Hexazo-p-rosanilin was an efficient and the most chromogenic coupler used in simultaneous as well as in postincubation coupling. With the latter localization is possible on the cellular (not subcellular) level.More chromogenic combinations are generally better for the cytospectrophotometrical measurement. The shape of extinction curves of azo-dyes produced with combinations studied was similar in models and in smears. In many combinations it was dependent on the presence of lipoproteins. A too steep decline of some curves prevented the use of some combinations in alkaline phosphatase determination with the two-wavelength method, even if they are very good in the qualitative studies and might be suitable for scanning cytospectrophotometry. p]The shape of extinction curves of azo-dyes produced in the reaction for acid phosphatase using hexazo-p-rosanilin as the coupling agent was independent of the presence of lipoproteins.The curves of azo-dyes produced in simultaneous coupling are not exactly the same as the curves obtained by postincubation coupling.In receipt of a fellowship of Netherlands Organization for the Advancement of Pure Research (Z.W.O.). Abbreviations used: AN-naphthol AS-AN phosphate; AS-naphthol AS-phosphate; B-Fast Blue B salt; BB-Fast Blue BB salt; BI-naphthol AS-BI phosphate; CL-naphthol AS-CL phosphate; DS-diazonium salt; GR-naphthol AS-GR phosphate; HP-hevazo-p-rosanilin; LB-Fast Red Violet LB salt; MX-naphthol AS-MX phosphate; S-substrate; TR-naphthol AS-TR phosphate (in the first half of the abbreviation), Fast Red TR salt (in the second half of the abbreviation); VB-4-amino-diphenylamine diazonium sulfate.     

Combined immunohistochemical staining for surface IgD and T-lymphocyte subsets with monoclonal antibodies in human tonsils

The aim of the present paper is to detect two different antigens simultaneously in a single slide. In cryostat sections of human tonsils, B-lymphocytes of follicle mantle-bearing surface IgD were immunostained with the alkaline phosphatase method using monoclonal anti IgD. The subsequent staining for T-lymphocyte subsets (T-helper and T-suppressor lymphocytes) was performed again with the alkaline phosphatase method using one of the monoclonal antibodies OKT 4, OKT 8, Leu 3a, Leu 2a. The best results with the alkaline phosphatase method were achieved using naphthol AS phosphate and Fast Blue BB for the revelation of the first antigen and naphthol AS-BI phosphate and diazotized New Fuchsin for the second.     

Light microscopic demonstration of myoid material in nuclei

Summary In the rabbit and bovine cornea the activity of alkaline phosphatase using histochemical as well as biochemical methods was investigated. Biochemically the enzyme activity was studied in separated corneal layers. In the histochemical investigation the best results were obtained in cryostat sections using the azocoupling method with naphthol AS-MX phosphate and Variamine Blue RT Salt. The enzyme activity was found not only in the epithelium and endothelium (as was described previously) but even in keratocytes. The mutual relation of activities in the epithelium and in keratocytes differed in both species. The overall activity found by histochemical methods is in good agreement with the biochemical determination of alkaline phosphatase (p-nitrophenyl phosphate as the substrate). Besides the histochemical approach shows an uneven distribution of alkaline phosphatase activity in individual cells which cannot be assessed by the biochemical determination.     

Cytochemical studies of the types and localization of acid phosphatases in the various regions of the midgut epithelium of Carausius morosus

Synopsis Cytochemical studies on the localization and substrate specificities of acid phosphatase activities in the epithelial cells of the midgut ofCarausius morosus have revealed the presence of two distinct types of phosphatases. Acid naphthol AS-BI phosphatase activity was present at particulate (lysosomal) sites in all regions of the midgut and its activity was particularly high in the pear-shaped organs. Acid -glycerophosphatase of low activity was present in the mid and posterior midgut regions, but was absent from the pearshaped organs. In the anterior region of the midgut, acid -glycerophosphatase activity could only be found associated with the concentrically laminated vesicles.     

Cytofluorometric quantification of the activity and reaction kinetics of acid phosphatase

Synopsis This paper describes how fluorogenic substrates derived from naphthol AS can be used for the microscopic demonstration and cytofluorometric quantification of the activity and reaction kinetics of acid phosphatase in single living cells.A special study has been made of acid naphthol AS-BI phosphatase. However, the method can be extended to other hydrolytic enzymes. The method is sensitive and accurate because: quantification of very low enzyme activity is possible; the reaction kinetics can be evaluated with a good degree of precision inasmuch as the initial reaction velocity is derived over short times; there is an absence of distributional error; and the errors due to extra-cellular diffusion of the hydrolysed substrate, to photo-decomposition, and to autofluorescence can be contained within very narrow limits.The procedures for determining enzyme activity and reaction kinetics, and the instrumental characteristics and devices required for carrying out these measurements, are described. Some possible applications are indicated.     

Quantitative histochemical investigation of semipermeable membrane techniques for the assay of acid phosphatase in skeletal muscle

Summary A post-coupling semipermeable membrane technique for determining the activity of acid phosphatase in sections of skeletal muscle has been developed and investigated for its reproducibility and validity. Cryostat sections of unfixed muscle mounted on dry dialysis membranes are first incubated for 1–4 h at 37° C on a gelled medium containing 4 mM naphthol AS-BI phosphate buffered at pH 5. They are next transferred to another gel containing only hexazotised Pararosanaline and incubated for a further 30 min. Finally, they are treated with 70% ethanol, dried in air, and mounted. The final reaction product (FRP) deposited within muscle fibres is mostly distributed as a fine reticular network, tentatively identified as sarcoplasmic reticulum. Large FRP granules of the kind observed with Meijer's simultaneous coupling membrane technique are not formed. The method is reproducible and valid in terms of several working criteria. For example, the mean absorbance of the FRP at its absorption maximum increases linearly with incubation time; and in model sections containing various amounts of a subcellular fraction rich in acid phosphatase, the mean absorbance after a constant incubation time is proportional to the enzyme concentration. FRP is formed at approximately twice the rate it is deposited in the simultaneous coupling method. The most important advantage of the post-coupling method over the simultaneous coupling method is that the inhibition of the enzyme by coupling reagents is avoided.     

Cytochemical localization of acid phosphatase and trimetaphosphatase activities in Kurloff cells

After stimulation of guinea pigs with estradiol to increase their Kurloff cell number, spleen imprints were prepared in order to detect non-specific acid phosphatase (AcPase) activity by light microscopic cytochemistry using naphthol AS-BI phosphate as substrate and pararosanilin or fast garnet GBC as coupler. For ultracytochemistry, Kurloff cells were prepared from spleens by filtration through a homogeneizer screen followed by repeated centrifugation. AcPase and trimetaphosphatase activities were tested using beta-glycerophosphate, cytidine-5'-monophosphate and inorganic trimetaphosphate as substrates. Significant enzymatic activities were demonstrated with all the substrates used in the cytoplasmic inclusion body of the Kurloff cells.     

Ultrastructural localization of anionic phospholipids in skeletal muscle plasma membrane

Summary A cytochemical study of acid phosphatase (AcPase) in the lateral prostate of the rat was performed to investigate whether AcP-ase in the secretory apparatus can be distinguished from AcP-ase in lysosomes and their related structures. Two types of AcP-ase were observed in the rat lateral prostate. One was found in the secretory apparatus (Golgi saccules and some Golgi vesicles, condensing and secretory vacuoles), and reacted well with naphthol AS-BI phosphate (N AS-BI P) as substrate; the other was found in the lysosomes and Golgi-associated endoplasmic-reticulum-lysosome system (GERL)-like structure, and reacted well with -glycerophosphate (GP) as substrate. Although the AcP-ase which reacted well with N AS-BI P was also observed in certain portions of pleomorphic lysosomes, it was concluded that it was the same as the AcP-ase found in the condensing and secretory vacuoles, since a lysosome engulfing a condensing vacuole was often observed. Therefore, it is concluded that the AcP-ase in the secretory apparatus in the rat lateral prostate is different from the AcP-ase in lysosomes. Condensing vacuoles appear to originate from particular portions of Golgi saccules, but not from the GERL or GERL-like structure, at least in the rat lateral prostate.     

Characterization and localization of an ATP diphosphohydrolase activity (EC 3.6.1.5) in sarcolemmal membrane from rat heart

In the present report we describe an ATP diphosphohydrolase (apyrase EC 3.6.1.5) in rat cardiac sarcolemma. It is Ca2+ dependent and is insensitive to ouabain, orthovanadate, N-ethylmaleimide (NEM), lanthanum, and oligomycin that are classical ATPase inhibitors. Sodium azide that is a mitochondrial inhibitor at low concentrations, did not affect the enzyme activity at 5.0 mM or below. In contrast, at high concentrations (> 10 mM) sodium azide inhibited the enzyme. Levamisole, a specific inhibitor of alkaline phosphatase and P1, P5-di(adenosine 5-)pentaphosphate (Ap5A), a specific inhibitor of adenylate kinase did not inhibit the enzyme. Mercury chloride showed a parallel inhibition of the hydrolysis of both substrates of apyrase. Similar inhibition profiles are powerful evidence for a common catalytic site for the hydrolysis of both substrates. The enzyme has an optimum pH range of 7.5–8.0 and catalyzes the hydrolysis of triphospho- and diphosphonucleosides other than ATP or ADP. The apparent Km (Michaelis constant) and Vmax (maximal velocity) are 62.1 ± 5.2 M and 1255.7 ± 178 mol inorganic phosphate liberated/min/mg with ATP and 59.4 ± 4.3 M and 269.2 ± 39 mol inorganic phosphate liberated/min/mg with ADP. Enzyme markers indicated that this apyrase is associated with the plasma membrane. A deposition of lead phosphate granules on the outer surface of the sarcolemmal vesicles was observed by electron microscopy in the presence of either ATP or ADP as substrate. It is suggested that the ATP diphosphohydrolase could regulate the concentration of extracellular adenosine, and thus is important in the control of vascular tone and coronary flow.     

Evaluation of histochemical observations of activity of acid hydrolases obtained with semipermeable membrane techniques

Summary Three distinct isoenzymes of acid phosphatase have been separated from extracts of m.gastrocnemius of normal and of vitamin E deficient rabbits by gel filtration and polyacrylamide gel electrophoresis. These isoenzymes, termed I, II and III, have molecular weights of: 110,000–130,000, 60,000–78,000 and 12,500–14,500. Isoenzymes I and II split the substrates 4-methylumbelliferyl phosphate and naphthol AS-BI phosphate and the activity is strongly increased in the muscles of vitamin E deficient rabbits. Isoenzyme III splits only 4-methylumbelliferyl phosphate and the activity is not increased in the muscles of vitamin E deficient rabbits. The pH-optimum for isoenzymes I and II is 4.8 and for isoenzyme III 5.5. It has been shown that the histochemical semipermeable membrane technique, using the substrate naphthol AS-BI phosphate, is a very reliable technique for demonstrating activity of the isoenzymes I and II in tissue sections. On the other hand, activity of isoenzyme III cannot be demonstrated with this histochemical technique. In pathologically altered muscles, the activity of the isoenzymes I and II is greatly increased whilst the activity of isoenzyme III is not significantly altered.This study was supported by a grant from the Prinses Beatrix Fonds, 's Gravenhage, The Netherlands and was partly extracted from the Ph.D. thesis of D.E. Israël (1977)     

Microspectrophotometric data on the kinetics of acid phosphatase activity in cells removed from the peritoneal cavity of the rat

Synopsis The extinctions (optical densities) of cells incubated for acid phosphatase in a histochemical azo-coupling procedure (naphthol AS-BI prosphate-hexazotized pararosaniline) have been measured microspectrophotometrically as a function of the incubation time and substrate concentration. A microcuvette was designed for the incubation. The amount of the reaction product in the cells at 23±1°C was found to be proportional to the incubation time for at least 40 min. Lineweaver-Burk plots were linear for some cells while in others nonlinear plots suggested the presence of two or more enzymes. This suggestion was supported by results obtained from polyacrylamide gel electrophoresis experiments.