Abstract
The activity of ornithine decarboxylase (ODC), the rate-limiting enzyme involved in the biosynthesis of polyamines, is markedly elevated in the adult rat heart 4 hr after isoproterenol or 24 hr after triiodothyronine treatment. The rate of degradation of ODC activity, measured after administration of cycloheximide, was not affected by these stimuli: half-lives of the enzyme remained between 18 and 24 min. After isoproterenol or triiodothyronine stimulation of adult rat heart, and in neonatal rats, kinetic data revealed the presence of a different form of the enzyme, with a Km of 30-50 µM, compared with 260 µM in the adult control. Pretreatment with actinomycin D did not prevent elevation of ODC activity caused by isoproterenol, nor did cyclic AMP appear to be involved in the ODC stimulation. These results suggest that heart ODC regulation involves mechanisms different from those seen in other tissues.
- Copyright © 1979 by Academic Press, Inc.
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