Polyamine biosynthesis in arginine-starved and refed rats
1991
Schertel, B. | Eichler, W.
Growth of rats fed with a synthetic diet was studied under control conditions (arginine-rich), arginine starvation, and arginine starvation/refeeding. Hepatic polyamine concentrations and ornithine decarboxylase (ODC-)activity were determined for each population. In the livers of arginine-starved rats putrescine was decreased to half the control content within 8 days; upon refeeding, it returned to control levels within another 8 days. Spermidine content in liver tissue of arginine-starved rats remained rather stable for 7 days, but thereafter dropped to half the original value within two days. Refeeding for a period of 11 days was not enough to restore the spermidine content. The effects of arginine starvation/refeeding on spermine were very similar to those of spermidine. ODC specific activity, when correlated with growth, was higher in livers of arginine-starved rats than in control animals. Refeeding caused a decrease in ODC-activity although growth arrest was completely, released. This apparent uncoupling of growth and ODC stimulation supports the theory that ODC in rat liver is regulated at three levels: first the growth-related component which is observed after stimulation by growth-hormone; second the known feed back control by polyamines, e,g. via antizyme, third the regulation at the level of the substrate supply which has been shown in this work. This is not a unique finding since very similar results have been obtained in previous experiments with the protozoan Tetrahymena thermophila. A remarkable observation of these assays was that L-ornithine, when added to the arginine-free diet was not able to substitute for L-arginine in directing growth and growth related processes.
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