Frontiers in Marine Science (Nov 2015)
Breakdown products of heme catabolism as senescence index in sea lamprey (Petromyzon marinus Linnaeus, 1758)
Abstract
Biliverdin and bilirubin are breakdown products of normal heme catabolism, caused by the body's clearance of aged red blood cells which contain hemoglobin. Bilirubin is created by the activity of biliverdin reductase on biliverdin, a green tetrapyrrolic bile pigment that is also a product of heme catabolism (bilirubin, when oxidized, reverts to become biliverdin once again). Bilirubin is then passed down the bile duct by way of the gallbladder into the intestine where further degradation and elimination occurs. Lamprey ammocoete larvae have a bile duct and a complete system for eliminate bilirubin, but the larvae undergo a phase of metamorphosis in which the larval gallbladder, the bile canaliculi of the hepatocytes, and all the intrahepatic bile ducts completely regress in a developmental process called lamprey biliary atresia, and bilirrubin accumulates in the liver. During the upstream spawning migration, liver colour of adults of Petromyzon marinus changes from orange-yellow to blue –green caused by gradual accumulation of biliverdin as the gonads develop. We analyzed the liver of 65 upstream migrants adults (32 recent migratory individuals and 33 at the end of four months stabled period) for the presence of the bile pigments, biliverdin and bilirubin, using levels of absorbance in a chloroform extract (650 nm biliverdin and 540 nm bilirubin) as indirect measure of their content. No significant differences were observed between sexes in the livers of recent migratory individuals. Nevertheless highest values of biliverdin/bilirrubin ratio were reached by females belonging to the group of older upstream migrants (mean: 2.33, sd: 0.53, Kruskal-Wallis test, p<0.05), but the liver weight of males was significantly higher than in females (mean males: 30.36 g, sd: 5.67; mean females: 17.38 g, sd: 5.87; Kruskal-Wallis test, p<0.05).
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