Purification and characterization of an NAD(+)-dependent dehydrogenase that catalyzes the oxidation of thromboxane B2 at C-11 from porcine liver. Development and application of 11-dehydro-thromboxane B2 radioimmunoassay to enzyme assay

11-Dehydro-thromboxane B2 has been identified as a major metabolite of infused as well as endogenous thromboxane B2 in mammalian plasma and urine. This metabolite is derived from thromboxane B2 by enzymatic oxidation at C-11 catalyzed by 11-hydroxythromboxane B2 dehydrogenase. A radioimmunoassay for 11-dehydro-thromboxane B2 has been developed and used for enzyme assay, purification and characterization. Antibodies were generated against 11-dehydro-thromboxane B2 conjugated to bovine thyroglobulin. Labeled marker was prepared by radioiodinating 11-dehydro-thromboxane B2-tyrosine methyl ester conjugate. A sensitive radioimmunoassay capable of detecting 10 pg of 11-dehydro-thromboxane B2 per assay tube was developed. The antibodies showed minimal crossreaction with thromboxane B2 (0.03%), prostaglandin D2 (2.76%) and other eicosanoids (less than 0.03%). The enzyme activity was determined by assaying NAD(+)-dependent formation of immunoreactive 11-dehydro-thromboxane B2 from thromboxane B2. The enzyme was found to be enriched in liver although significant activity was also detected in gastrointestinal tract and kidney in pig. The enzyme was purified from porcine liver cytosol to apparent homogeneity using conventional and affinity chromatography. The purified enzyme exhibited coenzyme specificity for NAD+ and used thromboxane B2 as a substrate. The enzyme also catalyzes NADH-dependent reduction of 11-dehydro-thromboxane B2 to thromboxane B2 indicating the reversibility of the enzyme catalyzed reaction. The apparent Km values for thromboxane B2, 11-dehydro-thromboxane B2 and NAD+ are 8.1, 8.0 and 23 microM, respectively. Subunit Mr was shown to be 55,000, whereas the native enzyme Mr was found to be 110,000 indicating that the enzyme is a dimer. The enzyme is sensitive to sulfhydryl inhibitions suggesting cysteine residues are essential to enzyme activity. The availability of a homogeneous enzyme preparation should allow further studies on the substrate specificity and the structure and function of the enzyme.     

Efficient purification of somatomedin-C/insulin-like growth factor I using immunoaffinity chromatography

Somatomedin-C/insulin-like growth factor I was purified from human plasma using a monoclonal antibody affinity column. Combining immunoaffinity chromatography with standard protein purification methods resulted in an overall recovery of 18%. The 35 micrograms of somatomedin-C/insulin-like growth factor I purified from 500 ml of plasma appeared as a single band when analyzed by polyacrylamide gel electrophoresis and could be used in radioimmunoassay and receptor binding studies.     

A solid-phase enzyme immunoassay of thromboxane B2

A solid-phase enzyme immunoassay for thromboxane B2 was developed using a conjugate of thromboxane B2 and beta-galactosidase. Anti-thromboxane B2 IgG was bound to a polystyrene tube, and the enzyme-labeled and unlabeled thromboxane B2 were allowed to react in a competitive manner with the immobilized antibody. Then, the specifically bound beta-galactosidase was assayed fluorimetrically, and the enzyme activity was correlated with the amount of unlabeled thromboxane B2. By using a calibration curve, thromboxane B2 was determined in the range of 20 fmol-14 pmol. 2,3-Dinor- and 2,3,4,5-tetranor-thromboxane B2 cross-reacted with thromboxane B2 to the extents of 18.6% and 0.4%, respectively. Most prostaglandins and their metabolites tested showed cross-reactivities of less than 1%. In application of the method to human blood and urine, an octadecylsilyl silica column was utilized for extraction and concentration of thromboxane B2. The crude extract contained a substance(s) which disturbed the enzyme immunoassay and gave an apparently high value of thromboxane B2, and the interfering substance was separated from thromboxane B2 by reverse-phase HPLC. Various amounts of authentic thromboxane B2 added to the purified material from human plasma could be determined by the enzyme immunoassay with a recovery of about 80% and the results correlated well with the values obtained by radioimmunoassay (r = 0.979). When the extract from human urine was analyzed by reverse-phase HPLC, the 2,3-dinor metabolite rather than thromboxane B2 was the predominant compound detected by the enzyme immunoassay.     

Tandem mass spectrometric determination of 11-dehydrothromboxane B2, an index metabolite of thromboxane B2 in plasma and urine

11-Dehydrothromboxane B2 is one of the major enzymatic metabolites of thromboxane B2 (TXB2), a biologically inactive product of thromboxane A2. The short half-life of thromboxane A2 and ex vivo production of thromboxane B2 by platelet activation make these prostanoid metabolites inappropriate as indices of systemic thromboxane biosynthesis, whereas 11-dehydro-TXB2 has been shown to reflect the release of thromboxane A2 in the human blood circulation. Analysis of 11-dehydro-TXB2 in plasma and urine was performed by gas chromatography-mass spectrometry-mass spectrometry using the chemically synthesized tetradeuterated compound as an internal standard. The high selectivity of triple-stage quadrupole mass spectrometry (tandem mass spectrometry) considerably facilitates sample purification as compared to single quadrupole mass spectrometric determination. Plasma concentrations in five healthy male volunteers were in the range 0.8-2.5 pg/ml. Urinary excretion of 11-dehydro-TXB2 was higher than that of 2,3-dinor-TXB2: 1.2 +/- 0.36 micrograms/24 h vs 0.53 +/- 0.33 micrograms/24 h (n = 5). Thus 11-dehydro-TXB2 appears at present to be the best index metabolite of systemic TXA2 activity in plasma as well as in urine.     

Enzyme immunoassay of thromboxane B2

An immunoassay for thromboxane B2 was developed in which the hapten molecule was labeled with beta-galactosidase. The immunoprecipitate formed after competition between enzyme-labeled and unlabeled thromboxane B2 was subjected to a fluorometric assay of beta-galactosidase. Thromboxane B2 was detectable in the range of 0.1-30 pmol. Both enzyme immunoassay and radioimmunoassay showed essentially the same cross-reactivities with other prostaglandins and their metabolites when the same antibody was used. Known amounts of thromboxane B2 were added to human plasma, and the sample was applied to an octadecyl silica column. The extract was analyzed by enzyme immunoassay to examine the correlation between the added (x) and measured (y) thromboxane B2 (y = 1.09x + 11.07 pmol/ml, r = 0.99). A satisfactory correlation was observed between radioimmunoassay (x) and enzyme immunoassay (y) (y = 0.92x + 4.64 pmol/ml, r = 0.96). The validity of enzyme immunoassay was also confirmed by gas chromatography-mass spectrometry of a dimethylisopropylsilyl ether derivative of thromboxane B2 methyl ester. The method was applicable to the assay of thromboxane B2 produced from endogenous precursor during thrombin-induced aggregation of human platelets.     

Metabolism of thromboxane B2 in the monkey.

[3H8]Thromboxane B2 was biosynthesized and infused into an unanesthetized monkey. Several urinary metabolites were isolated and their structures elucidated using gas chromatography-mass spectrometry. In addition to the major urinary metabolite, dinor-thromboxane B2, a series of metabolites resulting from dehydrogenetion of the alcohol group at C-11 were identified: 11-dehydro-thromboxane B2, 11-dehydro-15-keto-13,14-dihydro-2,3-dinor-thromboxane B2, and 11-dehydro-15-keto-13,14-dihydro-19-carboxyl-2,3,4,5-tetranor-thromboxane B2. 6-(1,3-dihydroxypropyl)-7-hydroxy-10-oxo-3-pentadecaenoic acid was also identified. Three mono-O-ethylated metabolites were formed from thromboxane B2, which in this study was infused in an ethanolic solution. A small quantity of thromboxane B2 was excreted unchanged into the urine.     

Determination of deoxynivalenol (DON) in blood, bile, urine and excrement samples from swine using immunoaffinity chromatography and LC-UV-detection

A work up procedure is described by which DON concentrations in blood, bile, urine and excrements from swine can be quantified by HPLC and UV- detection at λ = 220 nm. The central step thereby is the purification and concentration of DON by means of an immunoaffinity column. While, in our experiments, the quantification of DON in blood and urine was straightforward an additional purification step by a preparative HPLC run prior to immunoaffinity chromatography was needed when bile and excrements were investigated. However, when low DON concentrations in blood and urine are expected, a preparative HPLC run prior to immunoaffinity chromatography is recommended as well, because larger amounts of sample materials should be analyzed and more impurities interfere with the column proteins. In our study, using spiked samples, recoveries ranged from 75—90% and limits of detection were 0.01 to 0.02 μg/ml.     

Radioimmunoassay of 11-dehydrothromboxane B2 in human plasma and urine

Because of the discrepancy between the capacity of platelets to synthesize thromboxane B2 ex vivo and the actual synthetic rate in vivo, measurement of thromboxane B2 in plasma is highly influenced by sampling-related artifacts. We have developed and validated a radioimmunoassay for a major enzymatic derivative of thromboxane B2 with an extended plasma half-life, i.e., 11-dehydrothromboxane B2. The binding of the tracer is displaced by as low as 1 pg/ml of the homologous ligand, with a high degree of specificity for the open ring structure as well as for the omega side-chain. This method can detect changes in the plasma concentration and urinary excretion of 11-dehydrothromboxane B2 associated with stimulated short-term increases of thromboxane B2 secretion in the human circulation.     

Characterization of a monoclonal antibody that binds equally to all apolipoprotein and lipoprotein forms of human plasma apolipoprotein B. II. Isolation of apolipoprotein B-containing lipoproteins from human plasma

Monoclonal antibody ('Pan B' antibody) that binds equally to all major forms of human plasma apolipoprotein B was used in an immunoaffinity chromatography procedure to isolate apolipoprotein B-containing lipoproteins from hyperlipidemic human plasma. These lipoproteins were compared with lipoproteins in native plasma, with lipoproteins isolated by polyclonal antibodies and with lipoproteins isolated by the conventional ultracentrifugational method. Judged by the apolipoprotein and lipid composition, lipoproteins isolated with 'Pan B' antibody were virtually identical to those isolated by ultracentrifugation or polyclonal antibodies. Lipoproteins isolated by 'Pan B' antibody were comparable in size and shape to the lipoproteins in native plasma and to the lipoproteins isolated by polyclonal antibodies or ultracentrifugation. The immunoaffinity column with monoclonal 'Pan B' antibody retained all apolipoprotein B-containing lipoproteins and showed significantly higher capacity than polyclonal immunoaffinity column. The column with the highest capacity allowed the isolation from whole plasma of 0.144 mg of apolipoprotein B per ml of gel in less than 2 h.     

A new method using simple solid phase extraction for the rapid gas-chromatographic mass-spectrometric determination of 11-dehydro-thromboxane B2 in urine

A new gas-chromatographic mass-spectrometric method for the rapid determination of 11-dehydro-thromboxane B2 in urine, the major metabolite of systemic thromboxane formation, has been developed. Excellent sample clean-up was obtained in a single step by adsorption of 11-dehydro-TXB2 on phenylboronate cartridges, vigorous polar and organic washing and elution with an acidic methanol mixture. Then the pentafluorobenzylester trimethylsilylether derivative of 11-dehydro-TXB2 was formed and quantified in isotope dilution technique by negative chemical ionisation gas-chromatography tandem mass-spectrometry. The daughter fragments m/z 243/247 of the parent ion m/z 511/515 were monitored. Recovery was linear and quantitative over a wide range, accuracy was 95 + 7% and precision was 11% down to the very low pg range in biologic samples. Independent validation of this very fast extraction method with a reference method applying extensive sample purification with consecutive reversed and straight phase extraction, precolumn derivatisation, reversed phase high pressure liquid chromatography and tandem gas-chromatography mass-spectrometry gave excellent agreement of values. Values for 11-dehydro-TXB2 excretion in 8 healthy controls were 501 + 298 (range 231 to 1141) ng/g creatinin. Excretion was suppressed by aspirin, moderately elevated in heavy smokers (range 680 to 1540) and increased in patients with venous thrombosis or pulmonary embolism (2370 to 13350 ng/g creatinin). This rapid extraction method is useful for the highly specific and sensitive determination of 11-dehydro-TXB2 in large sample numbers.     

Presence of immunoreactive salusin-β in human plasma and urine

Salusin-α and salusin-β are multifunctional bioactive peptides originally identified using bioinformatics analyses. Salusin-β has been shown to exert potent hypotensive, bradycardic, and pro-atherosclerotic effects. The form in which it exists in biological fluids remains undetermined due to technical difficulties originating from its unexpected physicochemical properties. Here we show that salusin-β peptide adheres to polypropylene and polystyrene, so that the aliquoted peptide dissolved in distilled water may rapidly disappear from the solution. By circumventing these features and using an antibody against C-terminal portion of salusin-β, we have successfully established a specific radioimmunoassay suitable for detection of immunoreactive human salusin-β. We have characterized the molecular form of salusin-β in human plasma and urine. The assay detected immunoreactive salusin-β concentrations as low as 5 fmol/tube and the concentration required for 50% inhibition of binding was 122 fmol/tube. Cross-reactivities with salusin-α and other bioactive peptides were negligible. Reverse-phase high performance liquid chromatography coupled with the radioimmunoassay detection after extraction from plasma and urine and using an octyl-silica column, revealed a major immunoreactive component that co-eluted with authentic salusin-β. Salusin-β-like immunoreactivity in normal human urine ranged from 0.23 to 2.22 nmol/l (mean ± SD, 1.16 ± 0.84 nmol/l, n = 10). These data present the first evidence that salusin-β circulates and is excreted in its authentic form, thereby verifying the initially predicted processing sites for salusin-β in humans.     

Solid-phase extraction of urinary 11-dehydrothromboxane B2 for reliable determination with radioimmunoassay.

In this paper we elaborate a one-step procedure for the selective extraction of urinary 11-dehydrothromboxane B2 on octylsilyl silica cartridges for reliable determination with radioimmunoassay. The immunoreactivity profile of nonselectively extracted urine after HPLC separation showed that as much as 70% of the total 11-dehydrothromboxane B2 immunoreactivity comigrates with polar interfering material. Its amount could be considerably decreased using acetonitrile:water (18:82, v/v) as wash solvent before elution of 11-dehydrothromboxane B2 from the cartridge. Alternatively, very high immunoreactive purity was achieved without the preceding wash step by selective elution of the analyte with dichloromethane:hexane (70:30). After both optimized steps in the extraction procedure were combined, immunoreactivity was found only in HPLC fractions corresponding to the retention volume of authentic 11-dehydrothromboxane B2. The homogeneity of this immunoreactivity was confirmed by two-step HPLC separation. A significant correlation of values was observed between samples measured after extraction and those measured after subsequent HPLC purification. A high correlation was also found with concentrations determined by radioimmunoassay using four different antisera. The values of 24 h excretion of 11-dehydrothromboxane B2 in 10 male volunteers (595 +/- 114 ng/g creatinine, mean +/- SD) as well as the inhibitory effect of acetylsalicylic acid (80 +/- 13%) closely correspond with those reported in the literature. This selective extraction procedure provides a high validity in radioimmunoassay without requiring any further purification step.     

Affinity purification of β-endorphin-like material from NG108CC15 hybrid cells by means of the monoclonal β-endorphin antibody 3-E7

Neuroblastoma × glioma hybrid cells (NG108CC15) were examined for the presence of β-endorphin-like material. In order to differentiate this β-endorphin-like material from crude cell extract, a procedure for immunoaffinity chromatography was developed. The monoclonal antibody 3-E7 employed possesses the unique property of recognizing the N-terminal sequence of virtually all endogenous opioid peptides, but not their precursors. By means of this immunoaffinity procedure about 90% of exogenous β-endorphin was recovered from 10 ml phosphate buffered saline samples. Affinity chromatography served as first-step purification of crude NG108CC15 cell extract for the separation and concentration of β-endorphin-like material. The eluate of the immunoaffinity gel was subjected either to Sephadex gel filtration or to high pressure liquid chromatography. Under either condition, immunoreactive β-endorphin which eluted with synthetic β-endorphin was detected. The concentration in six different batches varied from 4 to 17 fmol/10⁸ cells. This would be 10–200-fold lower than that observed for the enkephalins or dynorphin A/α-neo-endorphin. It is concluded that the utilization of the monoclonal antibody 3-E7 for a first-step purification of cell extracts was an essential pre-requisite for the separation of β-endorphin-like material from the hybrid cells. The presence of enkephalin-like material, of dynorphin A/α-neo-endorphin-like material and of β-endorphin immunoreactive material suggests that NG108CC15 cells are able to generate opioid peptides related to the precursors pre-proenkephalin A, pre-proenkephalin B and pro-opiomelanocortin.     

Analysis of urinary 8-nitroguanine, a marker of nitrative nucleic acid damage, by high-performance liquid chromatography-electrochemical detection coupled with immunoaffinity purification: association with cigarette smoking

We have developed an analytical method to quantitate urinary 8-nitroguanine, a product of nitrative nucleic acid damage caused by reactive nitrogen species such as peroxynitrite and nitrogen dioxide. 8-Nitroguanine was purified from human urine using immunoaffinity columns with an anti-8-nitroguanine antibody, followed by quantitation by high-performance liquid chromatography-electrochemical detection. Four sequential electrodes were used to (a) oxidize interfering compounds (+250 mV), (b) reduce nitrated bases (two online electrodes at -1000 mV), and (c) quantitate reduced derivatives (+150 mV). Using this system 8-nitroxanthine can also be detected, with the detection limits being 25 and 50 fmol/injection for 8-nitroguanine and 8-nitroxanthine, respectively. The method was used to analyze both adducts in the urine of smokers (n=12) and nonsmokers (n=17). We found that smokers excrete more 8-nitroguanine [median, 6.1 fmol/mg creatinine; interquartile range (IQR), 23.8] than nonsmokers (0; IQR, 0.90) (p=0.018), and although 8-nitroxanthine was detected in human urine, its level was not related to smoking status. This is the first report to show that 8-nitroguanine is present in human urine and the methodology developed can be used to study the pathogenic roles of this adduct in the etiology of cancers associated with cigarette smoking and inflammation.     

Enzyme-immunoassay of thromboxane B2 at the picogram level

A highly sensitive and reproducible enzyme-immunoassay for the measurement of thromboxane B2 was developed. Thromboxane B2 (TxB2) was coupled with beta-D-galactosidase by mixed anhydride reaction. Thromboxane B2-antiserum was generated in rabbits and used at a final dilution of 1:480,000. The separation of immunocomplex from the free form of TxB2 was accomplished by the double antibody method. The second antibody was sheep anti rabbit IgG. The precipitated enzyme activity was measured fluorometrically with 4-methyl-umbelliferyl-beta-D-galactoside as substrate. This method allowed to measure TxB2 in the range of 0.002-5 picomole per tube. The cross-reactivity of the anti-thromboxane B2-antiserum with 2,3-dinor thromboxane B2 was about 20%, but it was less than 0.2% for the other prostanoids tested. TxB2 extracted from human urine was measured by enzyme-immunoassay (y) and radioimmunoassay (x) which has been found closely correlated to values obtained by gas chromatography-mass spectrometry. Regression analysis of the data comparing enzyme-immunoassay and radioimmunoassay gave the equation y = 0.996 x + 0.470, correlation coefficient r = 0.9947. Inter-assay coefficient of variation was 3.1%. The assay was further simplified by coating the second antibody on glass beads. The regression equation between this solid-phase enzyme immunoassay (y) and radioimmunoassay (x) was y = 0.9860 X 1.927, r = 0.9895, and enzyme immunoassay (y) was y = 0.9749 X -0.94808, r = 0.9887. Thus, the enzyme-immunoassay shows specificity and sensitivity comparable to radioimmunoassay making use of radioactive tracer unnecessary.     

硫氧还蛋白抗体柱的制备

目的:探索硫氧还蛋白(Trx)抗体柱对Trx融合蛋白纯化的可行性。方法与结果:对含有Trx基因的质粒表达载体pTrxFus进行改造,在Trx读框之后加入6×His序列,并在大肠杆菌中表达C端带有6×His标签的Trx,经Ni2+柱亲和纯化后制备多克隆抗体;把经蛋白A纯化后的抗体偶联在溴化氰活化的琼脂糖凝胶上,制成Trx抗体柱;用此抗体柱纯化与Trx融合表达的豇豆胰蛋白酶抑制剂(CpTI),SDS-PAGE结果显示获得了纯度较高的Trx-CpTI。结论:用Trx抗体制成的免疫亲和层析柱可以有效纯化Trx融合蛋白。     

Circulating and urinary thromboxane B2 metabolites in the rabbit: 11-dehydro-thromboxane B2 as parameter of thromboxane production

The metabolism of thromboxane B2 was studied in the rabbit. The aim of the study was to identify metabolites in blood and urine that might serve as parameters for monitoring thromboxane production in vivo. [5,6,8,9,11,12,14,15-3H8]-Thromboxane B2 was administered by i.v. injection to rabbits, and blood samples and urine were collected with brief intervals. The metabolic profiles were visualized by two-dimensional thin layer chromatography and autoradiography, and the structures of five major metabolites were determined using chromatographic and mass spectrometric methods. In urine the major metabolites were identified as 11-dehydro-TXB2 and 2,3,4,5-tetranor-TXB1, and other prominent products were 11-dehydro-2,3,4,5-tetranor-TXB1, 2,3-dinor-TXB1 and 2,3-dinor-TXB2. In the circulation, TXB2 was found to disappear rapidly. The first major metabolite to appear was 11-dehydro-TXB2, which also remained a prominent product in blood for the remainder of the experiment (90 min). With time, the profile of circulating products became closely similar to that in urine. TXB2 was not converted into 11-dehydro-TXB2 by blood cells or plasma. The dehydrogenase catalyzing its formation was tissue bound and was found to have a widespread occurrence: the highest conversion was found in lung, kidney, stomach and liver. The results of the present study suggest that 11-dehydro-TXB2 may be a suitable parameter for monitoring thromboxane production in vivo in the rabbit in blood as well as urinary samples, and possibly also several tissues. This was also demonstrated in comparative studies using radioimmunoassays for TXB2 and 11-dehydro-TXB2.     

A procedure for the rapid purification in high yield of human glucocerebrosidase using immunoaffinity chromatography with monoclonal antibodies

A novel chromatographic immunoaffinity procedure is described for the purification of Form I glucocerebrosidase (see J. M. F. G. Aerts, W. E. Donker-Koopman, M. K. Van der Vliet, L. M. V. Jonsson, E. I. Ginns, G. J. Murray, J. A. Barranger, J. M. Tager, and A. W. Schram, 1985, Eur. J. Biochem. 150, 565-574) from extracts of human tissues. The affinity support consists of two monoclonal anti-(glucocerebrosidase) antibodies immobilized by covalent coupling to CNBr-activated Sepharose 4B. After adsorption of the enzyme from a crude detergent extract, the column is washed successively with 30% ethylene glycol in citrate buffer (pH 6), 1% Triton X-100 in citrate phosphate buffer (pH 5.2), and 50% ethylene glycol in citrate buffer. The enzyme is eluted with 90% ethylene glycol in citrate buffer. After dilution to 30% ethylene glycol, the immunoaffinity purification is repeated. The procedure can be completed within less than 18 h. The final preparations have a high specific activity (50 U/mg protein (n = 4) for the placental enzyme) and contain no detectable impurities after polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The yield is high (81 +/- 8% for the placental enzyme). The immunoaffinity column has a high capacity, can be regenerated easily, and can be utilized repeatedly without loss of activity.     

An imbalance between prostacyclin and thromboxane in relation to cerebral blood flow in neonates with maternal preeclampsia.

OBJECTIVE: A disturbance of prostacyclin (PGI2) and thromboxane A2 (TXA2) balance has been reported in preeclampsia. However, little is known about the concentrations of these prostanoids in neonates born to preeclamptic pregnant women. The purpose of this study is to determine whether the PGI2 and TXA2 concentrations are altered and whether the prostanoid balance correlates to the cerebral blood flow in neonates born to preeclampsia. METHODS: Spontaneously voided urine samples were collected from 20 neonates of normotensive and 16 neonates of preeclamptic women during the first 24 h after birth. We measured by radioimmunoassay the concentrations of urinary 6-keto-prostaglandin F1alpha (6-keto-PGF1alpha) and 11-dehydro-thromboxane B2 (11-dehydro-TXB2), respectively. Blood flow velocity in the middle cerebral artery was studied by pulsed Doppler ultrasonography in the neonates between 17 and 38 h after birth. RESULTS: There was no significant difference between the urinary 6-keto-PGF1alpha in the neonates of mothers with and without preeclampsia (median, 5.3 vs. 3.6 ng/mg of creatinine). In contrast, the urinary 11-dehydro-TXB2 and the ratio of 11-dehydro-TXB2 to 6-keto-PGF1alpha in the neonates of mothers with preeclampsia were significantly lower as compared with the neonates without preeclampsia, respectively (13.7 vs. 20.6 ng/mg of creatinine and 3.0 vs. 5.2, median). The resistance index in the middle cerebral artery was significantly reduced in the neonates with preeclampsia than without preeclampsia (0.67 +/- 0.01 vs. 0.74 +/- 0.02, mean +/- SEM). CONCLUSIONS: There was an association between maternal preeclampsia and the imbalance in the neonatal urinary excretion of PGI2 and TXA2 metabolites. This imbalance may contribute to the regulation of cerebral blood flow.     

Immunoaffinity purification of the calpains

A monoclonal antibody to the small subunit common to both mu- and m-calpains can be used in an immunoaffinity column to purify either mu- or m-calpain in a proteolytically active form. Extracts in 150 mM NaCl, pH 7.5, are loaded onto a column containing the anti-28-kDa antibody; the column is washed with 500 mM NaCl, pH 7.5, and the bound calpain is eluted with 150 mM NaCl, 50 mM Tris-HCl, pH 9.5, and 1 mM EDTA. These elution conditions do not affect the proteolytic activity of either mu- or m-calpain. It is most efficient to reduce the volume and to remove any proteolytic activity from crude extracts by using successive phenyl Sepharose and ion-exchange columns before loading onto the immunoaffinity column. The column purifies m-calpain more effectively than mu-calpain; m-calpain is greater than 90% pure after a single pass through this column, whereas mu-calpain can be purified to >70% purity. The epitope for the monoclonal antibody is between amino acids 92 and 104 (numbers for human calpain) in the 28-kDa subunit. Evidently, this area is shielded in the calpain molecule in a way that affects binding of the antibody to the native molecule.