Regulation of ovarian ornithine decarboxylase. Role of calcium ions in enzyme induction in isolated swine granulosa cells in vitro

Johannes D Veldhuis

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

When swine granulosa cells were cultured in chemically defined medium selectively deficient in Ca2+, the dose-dependent stimulation of ornithine decarboxylase (EC 4.1.1.17) activity in response to prostaglandin E2, l-epinephrine or the somatomedin, multiplication-stimulating activity, was attenuated markedly. Putative calcium influx blockers, verapamil and diltiazem, also inhibited hormone-stimulated enzymic activity. Similar inhibitory effects were exerted by divalent (cobalt) or trivalent (lanthanum) cations believed to compete with calcium for extracellular binding sites. The suppressive effects of extracellular calcium deprivation were time-dependent (suggesting gradual depletion of intracellular calcium stores), and could be mimicked by the intracellular antagonist of calcium action, trifluoperazine. The mechanism(s) subserving diminished hormonal induction of enzyme activity could not be accounted for by alterations in cell viability, general protein synthesis, half-life of decay of enzyme activity (measured in the presence of cycloheximide), or apparent Km of ornithine decarboxylase. Ca2+ and/or calcium antagonists did not modify enzyme activity in cell-free preparations. These observations implicate Ca2+ in the hormonal induction of a discrete cytosolic enzyme in isolated intact ovarian cells.

Original languageEnglish (US)
Pages (from-to)211-216
Number of pages6
JournalBBA - Molecular Cell Research
Volume720
Issue number2
DOIs
StatePublished - Apr 29 1982
Externally publishedYes

Keywords

  • (Swine granulosa cell)
  • Ca
  • Enzyme induction
  • Ornithine decarboxylase

ASJC Scopus subject areas

  • Biophysics
  • Cell Biology
  • Molecular Biology
  • Medicine(all)

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