Effect of neonatal and adult testosterone treatment on the cellular composition of the adult female rat anterior pituitary

The adult female pituitary has significantly more lactotrophs than that of the male, while the later has a higher percent of somatotrophs. It is clear that GH and prolactin (PRL) gene expression and somatotroph and lacrotroph proliferacion are modulated by the postpubertal hormone environment; howev er, the role of the neonatal steroid environment in this process is not kno wn. We have used in Situ hybridization to determine the number of GH and PR L mRNA-containing cells, as well as the level of expression of these two ho rmones, in response to neonatal and adult testosterone treatment. Female ra ts exposed to testosterone during the neonatal period, adulthood or both pe riods, as well as normal females and males were used. Exposure to testosterone during the neonatal period significantly increased the percentage of somatotrophs (ANOVA: P<0.005) and decreased that of lact otrophs in the adult female rat (ANOVA: P<0001). Adult testosterone treatme nt had no significant effect on the percentage of somatotrophs. The percent age of lactotrophs was significantly increased by adult testosterone only i n those rats also exposed to neonatal testosterone. PRL mRNA concentrations , as reflected by silver grains/cell, were reduced by neonatal testosterone and increased by adult testosterone treatment (ANOVA: P<0.0001). Overall P RL mRNA levels, measured by densitometry,, were also reduced by neonatal te stosterone exposure, but adult testosterone had no effect (ANOVA: P<0.001). GH mRNA levels per cell, as reflected by silver grains/cell, were increase d by adult testosterone, while neonatal testosterone treatment had no effec t. Overall GH mRNA levels per unit area, determined by densitometry measure ments, were increased by both neonatal and adult testosterone treatment, wi th the combination of these two treatments resulting in adult females havin g levels indistinguishable from intact males (ANOVA: P<0.003). These results suggest that, in combination with postpubertal sex steroids, the neonatal gonadal steroid environment plays an important role in determi ning anterior pituitary hormone synthesis and cellular composition.