Adenosine Partially Prevents Cirrhosis Induced by Carbon Tetrachloride in Rats

Abstract

Adenosine administration was tested in rats with carbon tetrachloride-induced hepatic fibrosis and was able to partially prevent the enlargement of liver and spleen induced by the toxin. This amelioration of the hepatomegaly was accompanied by a 50% reduction of the liver collagen deposition and preservation of content of glycosaminoglycans. A stimulated hepatic collagenase activity is apparently the mechanism for reduction of collagen accumulation. These effects were associated with a striking improvement in liver function. Adenosine treatment did not modify the late hepatotoxic effect of the carbon tetrachloride; however, the stimulatory effect of the nucleoside on energy state appeared to counteract the drastic decreases in adenine nucleotides, ATP, ATP/ADP ratio and energy charge elicited by the hepatotoxin. Moreover, a possible beneficial action of enhanced hepatic oxygenation caused by the vasodilator properties of adenosine cannot be ruled out. Regardless of the mechanism, adenosine seems to change the cellular response to the injury induced by the hepatotoxin.

Adenosine reverses a preestablished CCl4-induced micronodular cirrhosis through enhancing collagenolytic activity and stimulating hepatocyte cell proliferation in rats

“…Serum albumin, bilirubin, aspartate transaminase (AST) (EC 2.6.1.1), and alanine transaminase (ALT) (EC 2.6.1.2) activities were determined as previously described. 13 Total liver collagen was extracted, as previously described in detail, 13 and quantified by its content of hydroxyproline according to the method reported by Rojkind and González. 18 Subcellular fractionation was performed as reported by Aguilar-Delfín et al 19 Whole homogenate was used to measure activity of prolyl hydroxylase (EC 1.1.1.1) by the technique modified by Camps et al, 20 whereas the cytosolic fraction was the source for assessing thymidine kinase (EC 2.7.1.21) activity according to Sauer and Willmanns.…”

“…Pellets were homogenized in absolute ethanol, and collagenous protein was extracted as previously described. 13 Collagen synthesis was then estimated according to the amount of ( 14 C)-hydroxyproline formed. 26 The collagenolytic activities of control and cirrhotic livers were assessed through 2 approaches.…”

“…The neutral collagenase activity was assayed as previously reported, using 1 mg of homogenate as source of enzyme activity. 13 In addition, liver collagenolytic ability to use endogenous substrates was determined essentially as described by Pérez-Tamayo et al 27 Here, 10 mg of homogenate protein was used as a source of both enzyme and homologous substrates. The final volume was 2 mL in both cases, incubated at 37°C for 24 hours.…”

“…Degraded collagen was separated by centrifugation from total collagen, and supernatants were hydrolyzed and quantified for hydroxyproline. 13 Collagenase activity was corrected by subtracting the value obtained in the presence of 10 mmol/l EDTA, and results were expressed as nanomoles of degraded collagen per hour per milligram of protein. 13 Northern Analyses.…”

“…Adenosine blocked the hepatosplenomegaly; re-duced by 60% the deposited collagen, largely ameliorating liver dysfunction; and promoted a striking increase in collagenase activity in the fibrotic liver. 13 The beneficial action of the nucleoside is also extended to preserve an adequate liver mitochondrial function, 14 and to maintain liver energy availability 13 and cell redox potentials, regulating the rate of collagen metabolism in vivo. 15 Adenosine was also able to stimulate liver cell proliferation in the CCl 4 -induced cirrhotic liver, an effect directly associated to the rate and subcellular location of lipoperoxidative events.…”