Monoclonal antibody-directed radioimmunoassay of specific cytochromes P-450

A rapid solid phase radioimmunoassay (RIA) for cytochromes P-450 has been developed utilizing specific monoclonal antibodies to major forms of rat liver cytochrome P-450 that are induced by 3-methylcholanthrene (MC-P-450) and phenobarbital (PB-P-450). Monoclonal antibodies (MAbs) that were endogenously labeled with [35S]methionine were used to detect MAb-specific cytochromes P-450 in liver microsomes from untreated rats and rats pretreated with 3-methylcholanthrene (MC) or phenobarbital. The competitive binding assays are rapid and can detect cytochrome P-450 in less than 100 ng of microsomal protein. The RIA was used to examine the distribution of MAb-specific cytochromes P-450 in extrahepatic tissues of MC-treated rats; an approximately 30- to 50-fold greater amount of MC-P-450 in liver relative to lung and kidney was observed, which corresponds well with aryl hydrocarbon hydroxylase activity in these tissues. The inducibility of MAb-specific cytochromes P-450 in several species was also examined by competitive RIA. Significant increases in the MAb-specific P-450 were observed in MC-treated rats, guinea pigs, and C57BL/6 mice, all highly inducible for aryl hydrocarbon hydroxylase; little increase was observed for the relatively noninducible DBA/2 mouse strain.

Monoclonal antibody-directed immunopurification and identification of cytochromes P-450

Several rat liver cytochromes P-450 have been substantially purified in a one-step immunoadsorption procedure using Sepharose-bound monoclonal antibodies (MAbs) to the major forms of rat liver cytochrome P-450 induced by 3-methylcholanthrene and phenobarbital (MC-P-450 and PB-P-450, respectively). When mixed with solubilized rat liver microsomes the immunoadsorbent based on the MAb to MC-P-450 binds two polypeptides of MW 56,000 and 57,000 while the immunoadsorbent made with the MAb to PB-P-450 absorbs a species of MW 54,000. These polypeptides are readily desorbed by 0.1 M glycine (pH 3.0). Isolation of MAb-specific cytochrome P-450 isozymes by this method has applications in numerous phases of cytochrome P-450 research.

Inhibition of 2-acetylaminofluorene oxidations by monoclonal antibodies specific to 3-methylcholanthrene-induced rat liver cytochrome P450

The inhibitory effects of ten monoclonal antibodies specific for methylcholanthrene (MC)-induced P450 were determined on both C- and N-hydroxylations of 2-acetylaminofluorene (AAF) by liver microsomes from rats pretreated with MC, phenobarbital as well as untreated animals. The inhibitory effects of these antibodies were also determined on AAF hydroxylations by purified rat liver MC-P450. The inhibition patterns of AAF hydroxylations with both microsomes and the purified P450 indicate that the formation of 7-OH-, 5-OH-, 3-OH-, 1-OH- and N-OH-AAF was catalyzed by the same unique isoenzyme or at least isoenzymes of common antigenic determinants.

Identification and quantitation of a 2.0-kilobase messenger ribonucleic acid coding for 3-methylcholanthrene-induced cytochrome P-450 using cloned cytochrome P-450 complementary deoxyribonucleic acid

We have used a plasmid containing DNA complementary to one of the two size classes of mRNA coding for 3-methylcholanthrene-induced cytochrome P-450 from rat liver to characterize and quantitate that mRNA. The plasmid used was constructed and identified as follows: Total poly(A+) RNA from 3-methylcholanthrene-induced liver was used as a template for cDNA synthesis. Double-stranded cDNA was inserted into plasmid pBR322 by the G-C tailing procedure. Recombinants were screened by colony hybridization using as probe [32P]cDNA prepared from partially purified cytochrome P-450 mRNA. A differential screening approach was used in which duplicate filters were hybridized with probe from either 3-methylcholanthrene treated or untreated rats. Plasmid p23 was strongly positive by colony hybridization. It was conclusively shown to contain cytochrome P-450 cDNA sequences by demonstrating that the mRNA which specifically hybridized to nitrocellulose-bound plasmid p23 could be translated in vitro into peptides that were immunoprecipitable with monoclonal antibodies specific for 3-methylcholanthrene-induced cytochrome P-450. The size and quantity of the mRNA complementary to plasmid p23 were determined by hybridization of the 32P-labeled plasmid to rat liver RNA that had been fractionated by electrophoresis under fully denaturing conditions and transferred to diazobenzyl-oxymethyl-paper. Plasmid p23 hybridized strictly to a single size of mRNA that was about 2000 nucleotides in length, the smaller of the two size classes of mRNA coding for 3-methylcholanthrene-induced cytochrome P-450. From this we concluded that, at least within the region of the mRNA contained within the insert of plasmid p23, the two size classes of 3-methylcholanthrene-induced cytochrome P-450 mRNA were very different in sequence. The mRNA complementary to plasmid p23 was increased about 4-fold after in vivo administration of 3-methylcholanthrene under conditions that result in maximal induction of 3-methylcholanthrene-induced cytochrome P-450 enzymatic activity. This increase in cytochrome P-450 mRNA parallels the increase in cytochrome P-450 enzymatic activity observed after 3-methylcholanthrene administration. These data suggest that the regulation of mRNA levels is an important point of control of cytochrome P-450 gene expression.

Phenotyping of cytochromes P-450 in human tissues with monoclonal antibodies

Cytochrome P-450 (P-450)-dependent aryl hydrocarbon hydroxylase (AHHase) and 7-ethoxycoumarin deethylase (ECDEtase) in human tissues were differentially inhibited by monoclonal antibodies (MAbs) that were prepared to inhibit and completely inhibited the activity of 3-methylcholanthrene-induced rat liver P-450. The AHHase and ECDEtase of placentas from individual women who smoked were inhibited by the MAbs by 83-90% and by 34-74%, respectively. Benz[a]anthracene (BaA)-induced AHHase and ECDEtase in lymphocytes were inhibited 18-65% and 30-78%, respectively. The enzymes in both control and BaA-induced human cells in culture were inhibited to different extents. Both the AHHase and ECDEtase in control and BaA-induced monocytes and in normal liver were largely unaffected by the MAb. Thus, we have with the MAbs: (i) identified P-450s with a common antigenic site in placenta, lymphocytes, and human cells in culture; (ii) identified two forms of hydrocarbon-induced P-450s in lymphocytes, at least one of which is common with the induced P-450s of placenta and with a P-450 form present in uninduced lymphocytes; (iii) identified two forms of P-450 responsible for smoking-induced ECDEtase activity in placenta, one of which is also responsible for AHHase activity; (iv) shown that the P-450s of liver, basal, and BaA-induced monocytes are different from the MAb-sensitive P-450s of placenta and lymphocytes; (v) quantitated in several human tissues the percentages of control and inducible AHHase and ECDEtase that are dependent on the MAb-sensitive P-450; and (vi) defined by HPLC the contribution of the MAb-sensitive P-450 to the formation of specific benzo[a]-pyrene metabolites. The results demonstrate the value of MAbs for defining antigenic site relatedness for different enzymatic functions of P-450s and for identifying and quantifying the amount of a specific enzyme activity in a tissue dependent on specific P-450s. This study may be a prototype for the use of MAbs for phenotyping and mapping of P-450s responsible for specific metabolic reactions and, thus, may be useful in determining the relationship of P-450 phenotype to individual differences in drug metabolism and carcinogen susceptibility.

Monoclonal antibodies to rabbit liver cytochrome P-450LM2 and cytochrome P-450LM4

Monoclonal antibodies were prepared from hybridoma clones isolated by the fusion of myeloma cells and spleen cells derived from mice immunized with either purified rabbit liver microsomal cytochrome P-450LM2 or cytochrome P-450LM4. Seven hybridoma clones produced three kinds of monoclonal antibodies to P-450LM2. The first class bound, precipitated, and inhibited the enzyme activity of P-450LM2 for both benzo[a]pyrene hydroxylation and 7-ethoxycoumarin deethylation. The other two classes either bound and precipitated or only bound the enzyme. These monoclonal antibodies to P-450LM2 showed a precipitin reaction and inhibition of enzyme activity that was specific for cytochrome P-450LM2. Thus, they did not react with or inhibit the enzyme activity of the other isozyme cytochrome P-450LM4, Fraction 1 or Fraction 7. All of the monoclonal antibodies formed against P-450LM2 were mouse immunoglobulin (Ig) subclass IgG1. The most effective monoclonal antibody strongly inhibited the formation of oxygenated metabolites of benzo[a]pyrene at various positions as well as the deethylation of 7-ethoxycoumarin. Four hybridomas were isolated which produced monoclonal antibodies to P-450LM4. One of the four was of the IgM class and three were of the IgG1 type. The four monoclonal antibodies bound to P-450LM4 but did not precipitate the enzyme, and did not bind to P-450LM2. The monoclonal antibody P-450LM4 complexes interacted with protein A, and the enzyme activity for benzo[a]pyrene hydroxylation could be removed by centrifugation. The high specificity and monoclonality of these antibodies suggest their potential usefulness for studying the genetics, regulation, and roles of the different isozymes of P-450LM in drug and carcinogen metabolism.

Effect of halothane, enflurane, and nitrous oxide on tracheal ciliary activity in vitro

Effects of halothane, enflurane, and nitrous oxide on ciliary beats were evaluated using a photoelectric system in dissected rabbit tracheal segments. Dose-dependent suppression of the frequency of ciliary beats of moderate degrees was observed after exposure of tracheal segments to warmed and humidified vapors of halothane and enflurane. No suppression, however, was noted after exposure to nitrous oxide. These findings suggest that halothane and enflurane directly suppress ciliary activity.

Isolation and characterization of glycoproteins from canine tracheal pouch secretions

Canine tracheal pouch secretions were solubilized with 1% sodium dodecyl sulfate and visualized by sodium dodecyl sulfate-agarose-acrylamide gel electrophoresis. Intact mucus, and water-soluble and insoluble fractions of mucus were shown to be composed of high molecular weight glycoproteins (Mr greater than or equal to 3 . 10(6)) and three major classes of proteins of lower molecular weight (Mr approximately 4 . 10(5), 2 . 10(5), and 6 . 10(4)). When the mucus secretions were further treated with a reducing agent, the glycoproteins were dissociated into subunits which appeared on the gel as three discrete bands. Separation of the high molecular weight glycoproteins from the other proteins was achieved by gel filtration on Biogel A-15m in the presence of 1% dodecyl sulfate following reduction and alkylation of mucus. These glycoproteins were further resolved, using DEAE cellulose chromatography in the presence of 6 M urea, into two protein fractions. Both fractions contained approximately 87% carbohydrate, high amounts of serine and threonine but differed significantly in contents of N-acetyl glucosamine and sialic acid; their mobility on gel electrophoresis was also different. Significant contents of cysteine were noted in both fractions. Results of this study indicate that the canine tracheal pouch preparations provide normal tracheal secretions which bear similarity in structure to the tracheobronchial secretions obtained from human patients.

Staphylococcal Enterotoxin A and C Production with Various Sugars as Energy Source 1

One percent added sugar (sucrose, maltose, lactose, glucose and glucose plus fructose) to casein hydrolysate (NAK) medium with or without starch or low methoxyl pectin did not significantly affect enterotoxin C production but did significantly decrease the pH at 12 and 24 h. The increased viscosity of colloidally thickened media resulted in decreased aeration in shaken cultures and decreased quantities of enterotoxin C. Sugars tested did not differ practically in their effects on the parameters of multiplying Staphylococcus aureus 361 and 265-1 which were measured. Addition of 1% of glucose, sucrose, or maltose prevented the decreased growth rate observed when strain 265-1 was grown in 20% O₂ + 80% N₂ instead of air.

An animal model of cigarette smoking in beagle dogs: correlative evaluation of effects on pulmonary function, defense, and morphology

Using beagle dogs, we have developed an animal model for the evaluation of the effect of chronic cigarette smoking on pulmonary defense and function and on lung structure. The smoking apparatus developed allows the dog actively to inhale properly diluted (1:4) smoke directly from the cigarette through a mouthpipe. In this model, 6-month and 1-year periods of mild to moderate smoking caused impairment of tracheal mucociliary transport and bacteriosuppressive activity of alveolar macrophages, with little change in pulmonary function. Morphologically, subtle, but significant, lesions were noted in the central airways and bronchiolar walls, consisting of tracheal epithelial basal cell hyperplasia, proliferation of goblet cells in central airways, and peribronchiolar infiltration by inflammatory cells. Morphometry of bronchiolar size distribution, volume proportion of parenchymal structure, and alveolar surface area, however, failed to show significant differences between the groups.

Hydrogenase and ribulose diphosphate carboxylase during autotrophic, heterotrophic, and mixotrophic growth of scotochromogenic mycobacteria

Two key autotrophic enzyme systems, hydrogenase and ribulose diphosphate carboxylase, were examined in Mycobacterium gordonae and two other chemolithotrophic, scotochromogenic mycobacteria under different cultural conditions. In all three organisms both enzymes were inducible and were produced in significant levels only in the presence of the specific substrate, hydrogen or carbon dioxide. M. gordonae exhibited increased growth rates and yields, indicating mixotrophic growth, in the presence of a number of single organic substrates, including acetate, pyruvate, glucose, fructose, and glycerol. In contrast to other aerobic hydrogen autotrophs, the presence of either acetate or pyruvate did not repress ribulose diphosphate carboxylase, and mixotrophic growth was rapid with these substrates. In the absence of carbon dioxide, growth in glycerol medium under an atmosphere of hydrogen and oxygen was severely inhibited, even with cells preadapted to heterotrophic growth on glycerol. Cyclic adenosine monophosphate was not effective in inducing hydrogenase or carboxylase in heterotrophic, mixotrophic, or hydrogen-inhibited cultures.

Severe pleural restriction: the maximum static pulmonary recoil pressure as an acid in diagnosis

Three patients with pleural restriction are presented in detail. One patient had had a right pneumonectomy and died of ventilatory failure due to left-sided restrictive pleurisy. The second patient had neoplastic pleural effusion and inactive tuberculosis. The third patient had systemic lupus erythematosus with bilateral restrictive pleuritis. The physiologic picture was similar in the three cases, with marked decrease of lung volumes, increase of the RV/TLC ratio, absence of airways obstruction, decrease of the Dco and decrease of dynamic lung compliance. In addition, each of these three patients and others with severe pleural restriction had a lower than normal maximum static pulmonary recoil pressure (Pmax). Since in pulmonary restrictive disease, the Pmax was found to be elevated, it was a useful test for distinguishing pulmonary restriction from pleural restriction.

D-Fucose as a gratuitous inducer of the L-arabinose operon in strains of Escherichia coli B-r mutant in gene araC

d-Fucose, a nonmetabolizable analogue of l-arabinose, prevents growth of Escherichia coli B/r on a mineral salts medium plus l-arabinose by inhibiting induction of the l-arabinose operon. Mutations giving rise to d-fucose resistance map in gene araC and result in constitutive expression of the l-arabinose operon. Most of these mutations also permit d-fucose to serve as a gratuitous inducer. It is concluded that d-fucose-resistant mutants produce an araC gene product with an altered inducer specificity. Addition of l-arabinose to cells induced with the gratuitous inducer, d-fucose, resulted in severe transient repression of operon expression followed by permanent catabolite repression. Transient repression but no permanent catabolite repression was obtained when cells unable to metabolize l-arabinose were employed. It is concluded that transport of l-arabinose alone is sufficient to achieve transient repression of its own operon, but that metabolism of l-arabinose must occur to achieve permanent catabolite repression of the l-arabinose operon. This general effect has been termed "self-catabolite repression."