RT Journal Article
SR Electronic
T1 Regulation of Rat Heart Ornithine Decarboxylase: Change in Affinity for Ornithine Evoked by Neuronal, Hormonal, and Ontogenetic Stimuli
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 504
OP 512
VO 16
IS 2
A1 CHRISTOPHER LAU
A1 THEODORE A. SLOTKIN
YR 1979
UL http://molpharm.aspetjournals.org/content/16/2/504.abstract
AB 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.