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Increasing evidence suggests that the naturally occurring polyamines, putrescine, spermidine, and spermine, play a role in the stability of cellular organelles, membranes, nucleic acids, and particles containing nucleic acid, e.g., ribosomes (see ref. 1). In addition to stabilizing cellular polyanions, polyamines also might affect directly the rate and extent of nucleic acid synthesis, probably by combining with nucleic acid products. Such a mechanism does appear to play a part in the stimulation by polyamines of bacterial DNA-directed RNA polymerase.2-4 Further, in regenerating rat liver there is a close correlation between the concentration of RNA and polyamines, as well as in the stimulation of synthesis of these compounds, as measured by incorporation of labeled precursors.5-7 A correlation in the accumulation of polyamines and nucleic acids has also been reported to occur in the developing chick embryo.8In the present work we have used the polyauxotrophic E. coli strain 15 TAU9to study the relationship between polyamines and nucleic acids in various nutritional conditions. It was shown earlier that by depriving this organism of an essential amino acid, the rate of RNA synthesis is reduced to about 10-15 per cent of normal.10' 11 Under these conditions the addition of chloramphenicol or streptomycin results in a stimulation in RNA synthesis. '11 12 In this communication it will be shown that deprivation of an essential amino

Concentrations of spermidine and spermine in fifteen different tissues of male and female rats aged three months were determined, using amido black as the quantitative reagent, after paper electrophoretic separation of the amines. The changes in the concentrations of these polyamines in relation to age were followed by determinations from six tissues of newborn rats and of male rats aged 1, 3 and 9 months. At the age of three months the largest amounts of the polyamines were found in the liver and the thymus, 900 to 1600 mμmoles of spermidine and 700 to 900 mμmoles of spermine per g wet weight. No great sex differences were observed. In most tissues the molar concentration of spermidine was higher than that of spermine. The spermidine content in every tissue studied decreased with increasing age, the fall being most marked during the first month of life. The spermine content as a rule increased somewhat during the first month and then remained nearly constant or decreased slightly. Consequently, the molar ratio spermidine/spermine was highest immediately after birth, decreasing in the liver, for instance, from 4.52 to 0.84 during 9 months. In the brain, in contrast to the other tissues investigated, it increased from 1.31 to 2.08 during the first 9 months.

The hepatic synthesis and accumulation of S-adenosylhomocysteine, S-adenosylmethionine and polyamines were studied in normal and vitamin B-6-deficient male albino rats. A method involving a single chromatography on a phosphocellulose column was developed for the determination of S-adenosylhomocysteine and S-adenosylmethionine from tissue samples. Feeding the rat with pyridoxine-deficient diet for 3 or 6 weeks resulted in a four- to five-fold increase in the concentration of S-adenosylhomocysteine, whereas that of S-adenosylmethionine was only slighly elevated. The concentration of putrescine was decreased to half, that of spermidine was somewhat decreased and that of spermine remained fairly constant. The activities of L-ornithine decarboxylase, S-adenosyl-L-methionine decarboxylase, L-methionine adenosyltransferase and S-adenosyl-L-homocysteine hydrolase were moderately increased. S-Adenosylmethionine decarboxylase showed no requirement for pyridoxal 5'-phosphate. The major effect of pyridoxine deficiency of S-adenosylmethionine metabolism seems to be a block in the utilization of S-adenosylhomocysteine, resulting in the accumulation of this metabolite to a concentration that may inhibit biological methylation reactions.