Abstract
Changes in the heme oxygenase activity of liver microsomes of bullfrog, Rana catesbeiana, during development, and the induction of the enzyme activity by administraiion of hemin or other reagents to the animal were studied in the context of the regulation of hemoglobin catabolism, An improved method for the determination of enzyme activity was also described. The results obtaiaed are as follows;
1.The standard method devised for the quantitation of bilirubin produced by the heme oxygenase reaction with crude samples involved the extraction of bilirubin with n-butanol and the coupling of the pigment with diazotized sulfonic acid.
2.The levels of NADPH-dependent heme oxygenase activity were similar in the liver microsomes of tadpole and adult bullfrog.
The Km for methemalbumin of the enzyme was about 2×10-5.×3. NADPH-de Dendent biliverdin reductase activity was found in neither the tadpole nor adult bullfrog liver, indicating that the final product of heme degradation in vivo in these animals is biliverdin.
4.The microsomal heme oxygenase activity increased 2-3 fold in the tadpole, liver prior to the onset of the conversion from tadpole to adult type of hemoglobin.
5.Injection of rnethemalbumin, phenylhydrazine, phenobarbital or triiodothyronine enhanced the heme oxygenase activity of both tadpole and adult bullfrog livers.
6.Actinomycin D inhibited the increase in the heme oxygenase activity with methemalbumin, while did not inhibit the increase with triiodothyronine.
7.The heme oxygenase activity of tadpole increased when the animal was kept two days in water at 25°C.
