Ontogeny of estradiol-2-hydroxylase activity in discrete brain areas of Wistar rats

Estradiol-2-hydroxylase activity was assayed radio-enzymatically in microsomes of six different brain areas of male and female Wistar rats between 22 and 77 days of age. The hypothalamus consistently showed the lowest activity and the hippocampus the highest, with the other areas falling in between. This pattern was seen in both sexes and at all the ages studied. In both sexes all six brain areas showed a steady increase in activity with increasing age. No statistically significant sexual differences in activity were observed for any area. The relatively low estradiol-2-hydroxylase activity in the hypothalamus is noteworthy since it contradicts the published evidence that this area has the highest in vitro catecholestrogen forming capacity in the brain.