The influence of nerve section on the metabolism of polyamines in rat diaphragm muscle

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Abstract
Concentrations of spermidine, spermine and putrescine were measured in rat diaphragm muscle after unilateral nerve section. The concentration of putrescine increased approximately 10-fold 2 days after nerve section and spermidine about 3-fold by day 3. An increase in the concentration of spermine was only observed after 7-10 days. It was not possible to show enhanced uptake of either exogenous putrescine or spermidine by the isolated tissue during the hypertrophy. Consistent with the accumulation of putrescine, activity of ornithine decarboxylase increased within 1 day of nerve section, was maximally elevated by the 2nd day and then declined. Synthesis of spermidine from [14C]putrescine and either methionine or S-adenosylmethionine by diaphragm cytosol rose within 1 day of nerve section and returned to normal or below normal values by day 3. Activity of adenosylmethionine decarboxylase similarly increased within 1 day of nerve section and declined to below normal by day 3. Activity of methionine adenosyltransferase was elevated throughout the period studied. The concentration of S-adenosylmethionine was enhanced during hypertrophy. Administration of methylglyoxal bis(guanylhydrazone) produced a marked increase in adenosylmethionine decarboxylase activity and a large increase in putrescine concentration but did not prevent the rise in spermidine concentration produced by denervation. Possible regulatory mechanisms of polyamine metabolism consistent with the observations are discussed.

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