Inhibitors of collagenolytic enzymes in the serum of patients with chronic liver disorders.

Abstract

SUMMARY Inhibitory effect of serum on collagenolysis was studied in rat hepatic slices. Sera of patients with cirrhosis contained low concentrations of inhibitors. Higher concentrations were found in sera from patients with chronic active hepatitis and chronic persistent hepatitis, than in healthy individuals. It is suggested that changes of the serum inhibitory activity are responsible for the control of collagen degradation in the injured liver.Chronic hepatic disorders are associated with accumulation of excess of collagen in the liver and hepatic fibrosis is important in the development of serious hepatic dysfunction. 1-3 Collagen degrading enzymes in fibrotic hepatic tissue have been studied by numerous investigators. It is generally accepted that collagen degradation is raised under conditions of fibrosis. Increased activity of collagenase,4 5 collagen peptidase6 7 and collagenolytic cathepsin8 9 has been described in the liver. It has been suggested that increased degradation of collagen is a defensive mechanism against fibrosis, but it is usually insufficient to successfully diminish the fibrotic process.8 10The mechanism of accelerated degradation of collagen fibres in the liver is unclear. Degradation of collagen needs the controlled action of a group of specific enzymes capable of selectively cleaving this fibrous protein. Received for publication 4 January, 1984 Methods PATIENTSThe study was done on 25 patients with hepatic cirrhosis (16 men: aged 43-61 years). Seventeen had chronic active hepatitis (eight women, nine men: aged 39-56 years), 23 had chronic persistent hepatitis (13 women, 10 men: aged 42-55 years), and 30 healthy individuals (23 men: aged 32-53 years).Blood was collected at 7 am after 10 hours of fasting. The sera were diluted with physiological saline in order to normalise the total protein concentration to 50 g/l. ANALYSISWistar rat liver slices prepared as for tissue culture were used. 13 It was found that these conditions were adequate for the investigations on living hepatic slices. 14 Collagen degrading enzyme activity was measured as hydroxyproline concentration liberated from collagen by enzymes presented in hepatic slices. Collagen degradation was determined according to Sopata et al. 15 In brief, rat hepatic slices (500 mg), reconstituted polymerised collagen fibres (5 mg), serum (05 ml) and 0-05M Tris-HC1 buffer pH=7.5 containing 0005M CaC12 and 0-2M NaCl were incubated for 18 h at 37°C. Control samples consisted of the same substances with potassium cyanate (005M) and collagenase inhibitor N-methyl maleimide (NMM), 1-25 ,tM. Control samples were used to allow for non-enzymatic liberation of hydroxyproline from collagen and to exclude the effect of the presence of hydroxyproline in the tested serum. Hydroxyproline was determined in the supernatant after acid hydrolysis with the 1364