Bile salt sulphotransferase activity in the liver of cholestatic infants.

A simple assay of bile salt sulphotransferase activity in human liver was developed. The system used glycolithocholate and PAPS as substrates. Km values for glycolithocholate and PAPs were 2.8 microM and 11.5 microM, respectively. Furthermore bile salt sulphation capacity in infants with cholestasis was investigated by measuring the activity of the bile salt sulphotransferase in the liver. No significant difference was found between the sulphotransferase activity in cholestatic infants and non-cholestatic adults. In addition the magnitude of the bile salt sulphotransferase activity in as neonatal liver did not differ from the enzymatic activity in adult liver. It is thus considered unlikely that low degree of sulphation of bile salts in infants is due to reduced capacity of this enzyme system.

Increased bronchial chloride concentration in cystic fibrosis.

Ten patients with cystic fibrosis (CF) and 10 patients with severe chronic bronchitis were analysed for bronchial electrolyte composition. Samples aspirated from the left main bronchus by a fibre-optic bronchoscope were dissolved in an iso-osmolar solution of N-acetylcysteine, and separated from cells and bacteria by gentle centrifugation. The concentrations of potassium and calcium were measured by flame emission and atomic absorption spectrometry, and found to be similar in both groups of patients. The mean concentration of chloride, measured by coulometric titration, was significantly higher in patients with CF than in patients with chronic bronchitis (170 vs. 85 mmol l-1, p less than 0.01). The findings are consistent with a functional abnormality of the chloride channels of the airway epithelium in patients with CF.

Composition and surface properties of the bronchial lipids in adult patients with cystic fibrosis.

Bronchial secretions from seven patients with cystic fibrosis (CF) were aspirated by fibreoptic bronchoscopy and analysed for lipid composition. The total lipid fraction was also used to measure dynamic surface tension. Pooled samples from 'normal' patients, healthy volunteers, patients with chronic bronchitis, and individual samples from two patients with bronchiectasis were used as controls. Increased bronchial inflammation and infection correlated with a decrease of the phospholipid fraction, and an increase of the cholesterol, diglyceride and triglyceride fractions. When individual phospholipids were analysed, patients with clinically severe CF showed a markedly decreased phosphatidylcholine fraction, whereas the phosphatidylinositol fraction was significantly higher in CF patients than in controls (p less than 0.05). Minimum surface tension was higher in CF patients compared to patients with chronic bronchitis (p less than 0.05). This might be related to earlier reported specific changes in the pattern of fatty acids of the CF bronchial phospholipids.

Increased mole fraction of arachidonic acid in bronchial phospholipids in patients with cystic fibrosis.

The fatty acid pattern of the phospholipids in the bronchial secretion of patients with cystic fibrosis (CF) showed an increase of the mole fraction of arachidonic acid (AA) in most phospholipid classes compared to normals. Increase of AA in some classes was also found in patients with chronic bronchitis and in patients chronically colonized with Pseudomonas aeruginosa but in the diphosphatidylglycerol, lysophosphatidylethanolamine and sphingomyelin phospholipids, high fractions of AA was found exclusively in CF patients. Arachidonic acid was found to attain the highest ratios in CF in seven of the nine major bronchial phospholipids compared to the controls. There was no difference in the ratio saturated/unsaturated fatty acids between the CF patients and the control groups. A tendency towards unsaturation of the fatty acids in the bronchial secretion seems to be characteristic of infection and inflammation but AA appears to be more markedly increased in CF. Thus, the recorded changes may be characteristic for CF and not secondary to infection and/or inflammation in general, nor to P. aeruginosa colonization.

Fatty acid hydroxylation in rat kidney cortex microsomes.

Rat kidney microsomes have been found to catalyze the hydroxylation of medium-chained fatty acids to the omega- and (omego-1)-hydroxy derivatives. This reaction, which requires NADPH and molecular oxygen, is a function of monooxygenase system present in the kidney microsomes, containing NADPH-cytochrome c reductase and cytochrome P-450K. NADH is about half as effective as an electron donor as NADPH and there is an additive effect in the presence of both nucleotides. Cytochrome P-450K absorbs light maximally at 452-3 nm, when it is reduced and bound to carbon monoxide. The extinction coefficient of this complex is 91 mM(-1) cm(-1). Electrons from NADPH are transferred to cytochrome P-450K via the NADPH-cytochrome c reductase. The reduction rate of cytochrome P-450K is stimulated by added fatty acids and the reduction kinetics reveal the presence of endogenous substrates bound to cytochrome P-450K. Both cytochrome P-450K concentration and fatty acid hydroxylation activity in kidney microsomes are increased by starvation. On the other hand, phenobarbital treatment of the rats has no effect on either the hemoprotein or the overall hydroxylation reaction and 3,4-benzpyrene administration induces a new species of cytochrome P-450K not involved in fatty acid hydroxylation. Cytochrome P-450K shows, in contrast to liver P-450, high substrate specificity. The only substances forming enzyme-substrate complexes with cytochrome P-450K are the medium-chained fatty acids and certain derivatives of these acids. The chemical requirements for substrate binding include a carbon chain of medium length and at the end of the chain a carbonyl group and a free electron pair on a neighbouring atom. The distance between the binding site for the carbonyl group and the active oxygen is suggested to be in the order of 16 A. This distance fixes the ratio of omega- and (omega-1)-hydroxylated products formed from a certain fatty acid by the single species of cytochrome P-450K involved. The membrane microenvironment seems also to be of importance for the substrate specificity of cytochrome P-450K, since removal of the cytochrome from the membrane lowers its binding specificity to some extent. A comparison between the liver and kidney cytochrome P-450 systems suggests that the kidney cytochrome P-450K system is specialized for fatty acid hydroxylation.