The answer is provided by Figure 3 (and partially by the top-ten Table 1) because here, the impact of individual chemicals on aromatase is
only conditioned by internal dose and inhibition potency.
responsible for the physiologic balance of androgens and estrogens.
stimulated both by FSH action on granulosa cells and by thecal androgens, the substrates for aromatase (Daniel and Armstrong 1980; Hillier and De Zwart 1981).
He insisted that his team's work filled in at least one piece of the puzzle by suggesting that the conversion of testosterone in the brain to oestrogen by the enzyme aromatase is
critical to developing and activating brain circuits that control male territorial behaviour.
This could have been caused by aromatase inhibition because the aromatase is
expressed in the uterus (36), and inhibition would thus lead to a reduced intracrine estradiol synthesis that subsequently must be "subtracted" from the estrogenic response induced by the administered potent estrogens (31,32).
Given the recent evidence that plasma estradiol and estrone levels are increased in atrazine-treated male Wistar rats (33), it is apparent that the presence of ovarian aromatase is
not essential for the effects of atrazine.
The two-factorial ANOVA showed that the activity of aromatase is
significantly different between males and females, and it also is different between sections of different areas of the brain, showing an interaction between the effect of these two factors ([F.sub.0.05(1),1,68] = 10.91, p = 0.001; [F.sub.0.05(1),16,68] = 10.4, p = 1.17 x [10.sup.-12]; and [F.sub.0.05(1),16,68] = 4.15, p = 1.74 x [10.sup.-5], respectively).