Study on the role of endogenous polyamines in glucagon, isoproterenol or serum-mediated induction of tyrosine aminotransferase in cultured heart cells.
In confluent and serum-starved embryonic heart cell cultures, the addition of serum (10%), glucagon (GLU, 0.1 microM) or isoproterenol (ISO, 10 microM), causes the onset of ornithine decarboxylase (ODC) activity, with a maximum after 5-6 hr. This is paralleled by polyamine accumulation and by the induction of TAT, which, in the case of GLU and ISO, exhibits maximal activity at 4-3 hr respectively, followed by a net decline. Cyclic AMP (cAMP) also accumulates after exposure to GLU or ISO. However, under different conditions of ODC inhibition, serum fails to induce TAT, thus supporting a relevant role of cellular polyamines in serum action. Conversely, cAMP and TAT responses to GLU or ISO are markedly improved under prevention of polyamine accumulation, which also leads to a longer lasting TAT inducibility. The suggestion is made that polyamines are not required in the cAMP-dependent mechanism of TAT induction, but rather in the restoration of the basal activity of the enzyme.
D000818:Animals; D001790:Blood Physiological Phenomena; D002478:Cells, Cultured; D002642:Chick Embryo; D003470:Culture Media; D000518:Eflornithine / Q000494:pharmacology; D004790:Enzyme Induction; D005934:Glucagon / Q000494:pharmacology*; D007545:Isoproterenol / Q000494:pharmacology*; D009206:Myocardium / Q000166:cytology / Q000201:enzymology*; D009955:Ornithine Decarboxylase / Q000378:metabolism; D065108:Ornithine Decarboxylase Inhibitors; D011073:Polyamines / Q000502:physiology*; D014444:Tyrosine Transaminase / Q000096:biosynthesis*
D003470:Culture Media; D065108:Ornithine Decarboxylase Inhibitors; D011073:Polyamines; D005934:Glucagon; D014444:Tyrosine Transaminase; D009955:Ornithine Decarboxylase; D007545:Isoproterenol; D000518:Eflornithine