The effect of neonatal administration of sex hormones on ribonucleic acid metabolism in the liver of male and female rats.

Fifteen minutes after the intraperitoneal injection of (32)P labelled phosphate, normal adult male rats show a higher incorporation of isotope into their liver nuclear RNA than do females. A single injection of testosterone into neonatal female rats causes a higher uptake of (32)P in adult life, while a single injection of oestradiol into male neonates lowers the incorporation in adult life. Gonadectomy at 4 weeks of age has only a small effect on the subsequent incorporation of (32)P into nuclear RNA either in control rats or in rats injected with sex hormones immediately after birth, showing that this effect of liver metabolism is mainly determined by the hormanal pattern at about the time of birth. The possible relevance of this sex difference in RNA metabolism to the different sex incidence of spontaneous or induced liver cancer is discussed.