The reduction in vitro in viscosity of mucoprotein solutions by a new mucolytic agent, N-acetyl-L-cysteine

Oral Fabrol (oral N-acetyl-cysteine) in chronic bronchitis

Five hundred and twenty-six patients suffering from chronic bronchitis were randomized to receive either N-acetylcysteine (NAC) or placebo during a 6-month period. The aim was to compare the number of acute exacerbations in the two groups. General practitioners were asked to enter patients with a diagnosis of chronic bronchitis, based on the MRC criteria. We failed to find any statistically significant difference in the number of exacerbations between the two treatment groups although there was a slight trend towards improvement in the NAC group during the first 3 months of the trial. The tolerability was similar for both treatments. Patients taking NAC showed a reduction in number of days on which they were incapacitated and this result was statistically significant.

Reduction of nonspecific fluorescence in respiratory specimens by pretreatment with N-acetylcysteine

Treatment of nasopharyngeal specimens with 0.25% N-acetylcysteine for 20 min at room temperature effectively reduced the nonspecific fluorescence encountered during direct examination of the specimens by immunofluorescence. The treatment did not affect specific antigen staining or the viability of several common respiratory viruses.

Pharmacokinetics of N-acetylcysteine in man

N-Acetylcysteine was given intravenously and as three fast dissolving and one slow-release formulation, on separate occasions, as a single dose of 600 mg to 10 fasting (5 men and 5 women) healthy volunteers. Blood and urine were sampled for the following 12 h. Renal clearance constituted around 30% of total body clearance, which was 0.21 l/h/kg. Volume of distribution was 0.33 l/kg, consistent with distribution mainly to extracellular water. The late elimination half-life was 2.27 h and the mean residence time 1.62 h. The slow-release tablet resulted in a flattened plasma concentration-time curve typical of slow release formulations, while the other three oral formulations were rapidly absorbed. The oral availability of N-acetylcysteine varied between 6 and 10%, with the slow-release tablet having the lowest and the fast dissolving tablet the highest availability.

The effects of mucus on the binding of cationized ferritin by human and animal gastrointestinal epithelium

Human gallbladder and gastric epithelial cells are normally covered with a layer of mucus. When specimens were exposed to cationized ferritin (CF) in vitro, they did not regularly bind nor internalise it. If the tissues were first exposed to the mucolytic agents cysteamine or pepsin, then the gallbladder epithelium readily bound CF and the gastric epithelium irregularly. The in vivo binding of CF by guinea pig gallbladder could be abolished by the induction of mucous hypersecretion by the antibiotic lincomycin. The removal of the mucus by mucolytic agents restored the binding of CF. The irregular binding of CF by gastric mucosa after the use of mucolytic agents suggests other factors may be at play.

Gorgosterol biosynthesis: localization of squalene formation in the zooxanthellar component of various gorgonians

Four species of gorgonians: three related pseudoplexaurids Pseudoplexaura porosa, P. flagellosa and P. wagenaari; and the unrelated Pseudopterogorgia americana, are sources of zooxanthellae capable, in purified broken cell preparations, of converting [14C]labeled farnesyl pyrophosphate into squalene. More extensive studies with P. porosa and P. americana zooxanthellae preparations characterize the conversion as enzymatic and demonstrate farnesyl pyrophosphate and reduced pyridine nucleotide as substrates. NADPH and NADH are essentially equivalent. Anaerobic conditions are not required. Despite numerous attempts zooxanthellae formation of sterols, including gorgosterol, from radioactive substrates was unsuccessful. By enzyme studies, we can show only the conversion of mevalonate into squalene as a zooxanthellae capability.

Ancillary medical therapy: help or hindrance

Aside from the more traditional methods of treating bronchial asthma, it has been the purpose of this review to consider some of the ancillary modes of therapy and to decide if they have a place in clinical practice. Regarding antihistamines, there is little evidence to support their therapeutic use in the management of asthma, but there is strong evidence for their safety in the treatment of allergic rhinitis or urticaria in asthmatic patients. Iodides have been used for years, but there is no good body of evidence to demonstrate their effectiveness. While they may be helpful in rare cases, one must be fully aware of their potential side effects and toxicity. Mucolytic agents induce bronchospasm and for the present should be contraindicated in asthma management. Of all ancillary modes of therapy, the anticholinergic agents seem the most promising. This is based on the theory of cholinergic mechanisms in asthma production as well as some clinical trials supporting this efficacy. Many of the problems of inhaled atropine have been eliminated with the development of atropinelike anticholinergic agents such as ipratropium bromide and oxytropium but unfortunately, none of these has been approved as yet for use in the United States.

Factors influencing the viscous properties of chicken tracheal mucins

1. Reduced viscosities, in water, of different types of mucin, such as fibrillar, gelatinous and soluble phase, separated from chicken tracheal secretions were measured. 2. H-bond breaking agents caused a significant decrease in the reduced viscosity of these mucins, but thiol-reagents alone did not have any effect. 3. Papain and Pronase did not cause any decrease in the reduced viscosity of these mucins. Neuraminidase decreased the reduced viscosity of soluble phase mucin by 50% by removing about 30% of its N-acetylneuraminic acid but had no effect on fibrillar and gelatinous mucins. Sulphatase neither removed any sulphate ester groups nor decreased the reduced viscosity. Due to some nonspecific intermolecular interaction, mixtures of mucins and enzymes or ovalbumin exhibited elevated reduced viscosities. 4. Ionic strength of the solutions appeared to decrease the reduced viscosity of these mucins. Increasing concentrations of Ca2+ in solutions of ionic strength of approx. 0.1 caused significant decrease in the reduced viscosity, but had no such effect in solutions of ionic strength of more than 0.1. 5. N-Acetylneuraminic acid and sulphate ester residues were 46.6 +/- 0.2, 43.4 +/- 0.6, 27.9 +/- 3.3 mg/g and 66.0 +/- 2.0, 34.2 +/- 3.3, 2.5 +/- 0.8 mg/g for fibrillar, gelatinous and soluble phase mucins, respectively. There appeared to be a good correlation between viscosity and N-acetylneuraminic acid contents among mucins of low reduced viscosities and between viscosity and sulphate ester residues among mucins of high reduced viscosities.

Effect of mucolytic pretreatment on gastric mucosal coating with barium sulfate in the rat. A scanning electron microscopic investigation

Freshly prepared isolated rat stomachs were used to examine the adherence of barium sulfate particles to the mucosal surface by scanning electron microscopy. The stomachs were pretreated with sodium bicarbonate alone or in connection with N-acetyl-L-cysteine and then treated with barium sulfate specially designed for double contrast examination of the stomach. The best adhesion of the contrast medium was obtained when the mucosa was pretreated with both the alkaline and mucolytic agent indicating that, for the optimum adherence of the contrast medium, the mucosal surface must be as clean as possible.

Pharmacokinetics of oral acetylcysteine: absorption, binding and metabolism in patients with respiratory disorders

The fate of an oral 100 mg dose of 35S-acetylcysteine, a mucolytic agent, was studied in 10 patients with respiratory disorders, 5 of whom underwent pneumonectomy or lobectomy a few hours after administration of the drug. In the 5 nonoperated patients, plasma radioactivity concentrations were maximal after 2 to 3 hours and remained high after 24 hours; about 22% of radioactivity was excreted in urine after 24 hours. In the 5 operated patients, plasma radioactivity concentrations were comparable with those in the nonoperated patients. Lung tissue radioactivity concentrations after 5 hours were comparable with those in plasma, while the presence of small amounts of radioactivity in the bronchial secretions indicates that acetylcysteine passes into the mucus. Total radioactivity after 5 hours consisted of free, unchanged drug and metabolites (about 22% of total in plasma, 48% in lung tissue), unchanged drug bound to protein by means of labile disulphide bridges (about 14% in plasma, 47% in lung tissue), and drug firmly bound to protein (about 64% in plasma, 5% in lung tissue). Oral acetylcysteine is rapidly absorbed and slowly excreted and is available in the lung in an active form for at least 5 hours at high concentrations.

A double-blind parallel study of acetylcysteine-isoproterenol and saline-isoproterenol in patients with chronic obstructive lung disease

A double-blind parallel study in patients with asthma compared the safety and efficacy of saline-isoproterenol (SI) and acetylcysteine-isoproterenol (AI), when administered at home as an aerosol, over a one-week period, using a conventional nebulizer compressor. Measurements of pulmonary function revealed statistically significant differences between the two therapies for FEV1 and FVC in favour of AI. In the group treated with AI, the average sputum viscosity after six days of treatment was significantly less than pre-treatment values, or when compared to the results with SI treatment. No serious side-effects were reported during treatment with either therapy. These results indicate that acetylcysteine combined with a bronchodilator, such as isoproterenol, may be safe and of significant value in the treatment of patients with asthma who are also sputum producers.

Characterization of gastric mucoproteins isolated by equilibrium density-gradient centrifugation in caesium chloride

1. The mucoprotein from pig gastric mucus has been purified by equilibrium centrifugation in a CsCl gradient. 2. This procedure removes the non-covalently bound protein, which is closely associated with the mucoprotein and not easily removed from it by gel filtration. 3. The purified mucoprotein is separable by gel filtration into a high-molecular-weight mucoprotein A (mol.wt. 2.3x10(6)) and a low-molecular-weight mucoprotein B/C (mol.wt. 1.15x10(6)). 4. These two mucoproteins have the same chemical analysis namely fucose 11.3%, galactose 26%, glucosamine 19.5%, galactosamine 8.3% and protein 13.6%. 5. Mucoprotein A contains 3.1% ester sulphate. 6. These mucoproteins are isolated without enzymic digestion and have a higher protein content than the blood-group-substance mucoproteins from proteolytic digestion of gastric mucus. Detailed amino acid analysis shows that the extra protein in the non-enzymically digested material is composed of amino acids other than serine and threonine. 7. Mucoproteins A and B/C contain respectively 130 and 9 half-cystine residues per molecule of which about 78 and 6 residues are involved in disulphide linkages. 8. Cleavage of these disulphide linkages by mercaptoethanol splits both mucoproteins into four equally sized subunits of mol.wt. 5.2x10(5) for mucoprotein A and 2.8x10(4) for mucoprotein B/C. 9. The sole N-terminal amino acid of mucoprotein A is aspartic acid, whereas mucoprotein B/C has several different N-terminal amino acid residues.

Isolation of chick intestinal nuclei. Effect of vitamin D3 on nuclear metabolism

1. Chick intestinal nuclei were isolated, with practically no contamination from other organelles and whole cells, by centrifugation through 2.4m-sucrose. 2. The proportions of RNA, DNA and protein of the isolated nuclei were unaffected by the vitamin D status of the birds. The RNA/DNA ratio was 0.15. 3. The incorporation of [5-(3)H]orotic acid into the rapidly labelled intestinal nuclear RNA, after a 10min. pulse of the orotic acid, was increased in vitamin D-deficient chicks only 10min. after a 125mug. dose of cholecalciferol. 4. There was no stimulation of the DNA-dependent RNA polymerase activity of the isolated nuclei from birds treated with cholecalciferol. 5. The results are discussed in relation to the changes occurring during the lag period, after administration of cholecalciferol and before Ca(2+) transport is detected, and the function of the vitamin.

Rheological assessment of mucolytic agents on sputum of chronic bronchitics

In vitro and in vivo studies were made on the sputum of chronic bronchitics using a Ferranti-Shirley cone and plate viscometer and a new stress relaxation method. The latter utilized a modified chemical balance and permitted study at very low shear rates. The results from simpler apparatus correlated well with the data obtained with the cone and plate viscometer. Significant reduction in four chosen parameters of viscosity occurred in vitro with N-acetylcysteine and with ascorbic acid-hydrogen peroxide-cupric ion complex (A.A.H.Cu.), but not with 4-molar urea. In vivo studies showed that, using freshly prepared A.A.H.Cu in an efficient hospital nebulizer, a statistically significant reduction in the four viscosity parameters occurred with subjective ease of expectoration. Nebulization of A.A.H.Cu performed with a simpler domestic-type nebulizer did not produce satisfactory reduction of viscosity or ease of expectoration. Rheological methods previously employed to study mucus and mucolytic agent activity are briefly reviewed.