Deoxyribonucleic acid and polyamine synthesis in rat ventral prostate. Effects of age of the intact rat and androgen stimulation of the castrated rat with testosterone, 5α-dihydrotestosterone and 5α-androstane-3β, 17β-diol

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Abstract
The relationship between polyamine synthesis, growth and secretion in vivo was examined in ventral prostates from: intact rats aged 3-60 wk; animals castrated for 7 days before injection with 5.alpha.-dihydrotestosterone (17.beta.-hydroxy-5.alpha.-androstan-3-one), testosterone and 5.alpha.-androstane-3.beta.,17.beta.-diol for up to 10 days; rats injected with the 3.beta.,17.beta.-diol immediately after castration. Ornithine decarboxylase activity and the concentrations of putrescine, spermidine and spermine were measured. DNA-synthetic activity was monitored by measuring [125I]iododeoxyuridine incorporation. An enhanced spermidine/spermine molar ratio reflected increased activity of the prostate. The ratio was higher (> 2) in prostates from sexually immature animals, than in the intact adult (1.5), suggesting that the ratio was indicative of the proliferative activity of the tissue. In the androgen-stimulated castrated rat, enhanced spermidine/spermine ratios tended to correlate with hypertrophy and secretion. In both sets of experiments there was a linear relationship between protein and spermidine content. High spermidine/spermine molar ratios were the consequence of a relatively low rate of accumulation of spermine relative to spermidine and protein. The relationship between polyamine synthesis and DNA-synthetic activity was investigated in cultured prostate. A combination of insulin (3 .mu.g/ml) and testosterone (0.1 .mu.M) caused a stimulatory response in the incorporation of [125I]iododeoxyuridine and in cell division, despite a depleted polyamine content and low ornithine decarboxylase activity in the cultured tissue.

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