(1968) reported that the administration of testosterone to newborn female rats increased the incidence of N-hydroxy-2-fluorenylacetamide-induced hepatic tumours, whereas oestradiol given to newborn male rats decreased the subsequent incidence of tumours. T-he mechanism whereby the hormonal environment of the neonate affects the sensitivity of the liver to carcinogens throughout life is unknown. Many changes in liver metabolism occur, and the present study is concerned with one that might be relevant to the problem of careinogenesis, namely, the effect of hormonal manipulation in the neonatal period on the turnover of liver nuclear RNA in adult life.
MATERIALS AND METHODSAnimal&-Male and female n'ewborn Wistar rats were randomly allocated to each experimental group and received a single subcutaneous injection of 500 /tg. of testosterone propionate or 250 #g. of oestradiol benzoate in 0-05 ml. arachis oil within 24 hours -after birth. Immediately upon withdrawal of the needle the injection site was sealed with colourless octaflex (1% w/w octaphonium chloride) to prevent leakage of the injected flu'id. Control groups were either given arachis oil or received no treatment. The young were weaned at 4 weeks of age and half of * Present address:
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