Increase In Polyamine Concentration Research Articles

Increases in brain polyamine concentrations in chemical kindling and single convulsion induced by pentylenetetrazol in rats

Concentrations of the polyamines, putrescine, spermidine and spermine were investigated in rat brains, in which chemical kindling or single convulsion had been induced by intraperitoneal injection of pentylenetetrazol (PTZ). A single injection of 60 mg/kg of PTZ produced tonic-clonic convulsion and increased the putrescine concentration 8 h after the injection. At lower doses of PTZ (10 and 30 mg/kg), neither marked behavioral seizure nor significant change in any polyamine concentration was observed. On the other hand, repeated injections of 30 mg/kg of PTZ eventually resulted in intense motor seizures (PTZ kindling) and increased the concentrations of all three polyamines. The most marked increase was detected in putrescine 1–48 h after the intense seizures. The increase in putrescine was clearly higher in PTZ kindling than in single convulsion. These results suggest that increases in polyamine concentrations are involved in neuronal excitability in the epileptic brain.

Polyamine Concentrations and Activities of Ornithine and Arginine Decarboxylase in Wheat Infected with the Stem Rust Fungus

Summary Inoculation of the first leaves of wheat ( Triticum aestivum L.) with the black stem rust fungus, Puccinia graminis f.sp. tritici Erikss & E. Henn., resulted in substantial increases in polyamine concentrations. Thus, several-fold increases in the concentrations of putrescine, spermidine and spermine were detected in rusted leaves. The activity of arginine decarboxylase in rusted leaves was small and rust infection caused a reduction in activity. Ornithine decarboxylase activity (both cytosolic and bound) was not detectable in healthy first leaves, but small increases in activities of both forms of ODC were detected in rust-infected leaves. Most of the increased polyamine concentration observed in whole leaves was localized in fungal pustules, although polyamine levels were also increased in regions between pustules. Similarly, activities of cytosolic and bound ODC were highest in pustule regions, with much lower activities in regions between pustules. It is likely that increased ODC activity in pustule areas represents fungal ODC.

Feedback control of ornithine decarboxylase expression by polyamines. Analysis of ornithine decarboxylase mRNA distribution in polysome profiles and of translation of this mRNA in vitro

Cell growth and differentiation require the presence of optimal concentrations of polyamines. Ornithine decarboxylase (ODC) catalyses the first and rate-controlling step in polyamine synthesis. In studies using cultures of Ehrlich ascites-tumour cells, we have shown that the expression of ODC is subject to feedback regulation by the polyamines. A decrease in the cellular polyamine concentration results in a compensatory increase in the synthesis of ODC, whereas an increase in polyamine concentration results in suppression of ODC synthesis. These changes in ODC synthesis were attributed to changes in the efficiency of ODC mRNA translation, because the steady-state amount of ODC mRNA remained constant. We now show that the number of ribosomes associated with ODC mRNA is low, and that the increase in ODC mRNA translation takes place without a shift in the distribution of ODC mRNA towards larger polysomes. This finding indicates that the polyamines regulate the efficiency of ODC mRNA translation by co-ordinately affecting the rates of initiation and elongation. By analysing ODC mRNA translation in vitro, using a rabbit reticulocyte lysate, polyadenylated RNA from a cell line with an amplified ODC gene, and a monospecific anti-ODC antibody, we also show that spermidine, but not putrescine, exerts a direct regulatory effect on ODC synthesis.

Polyamines and nucleic acid metabolism in chick embryo. Incorporation of labelled precursors into nucleic acids of subcellular fractions and polyribosomal patterns

1. An increase in polyamine concentration, caused by inhibiting the amine oxidase activities with iproniazid, increased the incorporation of [(3)H]orotic acid into chick-embryo RNA and DNA. On the other hand, a decrease in polyamine concentration, obtained by causing an increase in amine oxidase activities, decreased [(3)H]orotic acid incorporation into nucleic acids. This was particularly evident for nuclear DNA and ribosomal RNA. 2. Polyribosomal patterns obtained by sucrose-density-gradient centrifugation showed highest radioactivity in the regions of 259s and 280s aggregates in those embryos in which the polyamine contents were enhanced, whereas a decrease in the radioactivity was observed when the polyamine concentrations were decreased. 3. The activity of DNA-dependent RNA polymerase, assayed in the same experimental conditions, also varied in the same fashion with changes in polyamine concentration.