Alterations in enzyme and cytochrome profiles of Rana catesbeiana liver organelles during thyroxine-induced metamorphosis. Changes in membrane-localized phosphohydrolases, oxidoreductases, and cytochrome levels in response to in vivo thyroxine administration

• Published in: The Journal of biological chemistry Vol. 251; no. 20; pp. 6161 - 6169
• Main Authors: Brucker, R F, Cohen, P P
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 25-10-1976
• Subjects: Animals; Cell Nucleus - enzymology; Cytochromes - metabolism; Kinetics; Liver - drug effects; Liver - enzymology; Membranes - drug effects; Membranes - enzymology; Metamorphosis, Biological - drug effects; Oxidoreductases - metabolism; Phosphoric Monoester Hydrolases - metabolism; Rana catesbeiana; Spectrophotometry; Thyroxine - pharmacology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(20)81838-9

A primary objective of the present study has been to determine the changes which occur in Rana catesbeiana liver organelle
membranes during thyroxine-induced metamorphosis. To this end, enzyme and cytochrome profiles were determined for mitochondria,
microsomes, and nuclear membrane fractions isolated from livers of R. catesbeiana tadpoles which had been fasted for 6 days
at 15 +/- 0.5 degrees and then immersed in thyroxine, 2.6 X 10(-8) M, for periods of up to 12 days at 23.5 +/- 0.4 degrees.
The ratio of total succinate-cytochrome c reductase activity in the initial homogenate fraction to the total activity of this
mitochondrial "marker" enzyme recovered in the final mitochondrial fraction remained constant, approximately 0.5, throughout
the course of thyroxine treatment; however, after a 3- to 4-day latency the mitochondrial protein mass recovered per unit
mass of initial homogenate protein was found to increase significantly (approximately 2-fold by Day 10 of thyroxine treatment).
A similar increase was also observed in the yield of microsomal, but not nuclear membrane, protein mass as a function of thyroxine
treatment. Prolonged thyroxine treatment (12 days) resulted in approximately 50% decreases in tadpole liver homogenate and
microsomal NADH-cytochrome c reductase specific activities; in contrast, mitochondrial and nuclear membrane NADH-cytochrome
c reductase specific activities were not altered under the same conditions. In addition, homogenate and microsomal NADPH-cytochrome
c reductase specific activities were found to have increased significantly after 12 days of thyroxine treatment; however,
the specific activity of NADPH-cytochrome c reductase in the mitochondrial fraction was unchanged. It was also observed that
thyroxine treatment resulted in increases in homogenate and microsomal glucose-6-phosphatase specific activities, whereas
the mitochondrial as well as nuclear membrane glucose-6-phosphatase specific activities remained unchanged. Furthermore, in
contrast to homogenate and mitochondrial monoamine oxidase specific activities, which decreased 30 and 40%, respectively,
as a consequence of thyroxine treatment (12 days), the succinate-cytochrome c reductase and oligomycin-sensitive Mg2+ ATPase
specific activities determined for these fractions increased significantly. In all instances, changes as a result of thyroxine
treatment in membrane-localized homogenate or organelle enzyme specific activities were apparent only after a 3- to 4-day
initial latent period. The in vitro effects of thyroxine (10(-10) - 10(-5) M) on the membrane-localized enzyme activities
examined in this study were either negligible or, as in the case of mitochondrial succinate-cytochrome c reductase and microsomal
NADH-cytochrome c reductase, opposite to the changes observed in response to in vivo thyroxine treatment, with the exception
of microsomal NADPH-cytochrome c reductase activity which was enhanced approximately 2-fold by 10(-5) M thyroxine...