Localisation of aromatase activity in androgen target areas of the mouse brain.
Oestrogens are formed from androgens in the mouse brain, but the localization of aromatase activity is unresolved. Immunocytochemistry has not detected aromatase in expected key androgen target areas such as the medial preoptic area. Using a micropunch method and a sensitive in vitro 3H2O product detection assay, we report significant aromatase activity in adult male preoptic area (POA) and amygdala with [1 beta-3H]testosterone as substrate (Vmax < or = 1,200 fmol 3H2O formed/mg protein/h), in contrast to cerebrum (Vmax < 18 Units), from two strains of albino mice (BALB/c, Swiss NIHS) and the wild-type, Mus musculus. Aromatase activity was significantly higher in the amygdala than in the POA, particularly in the Swiss NIHS (4.6 x higher). Neonatal preoptic aromatase activity is 4 times higher than in the adult, but the Kms (both approximately 30 nM) suggest that the enzyme does not change during development. Similar inhibition potencies using Fadrozole HCl (IC50 approximately 0.5 nM) also suggest a common form of the enzyme in adult and developing brain. Adult mouse ovarian aromatase activity is higher (Vmax > 3,000 Units), but has a substrate binding constant similar to that of the POA.
Wozniak
A
A
MRC Neuroendocrine Development and Behaviour Group, Institute of Animal Physiology and Genetics Research, Babraham Cambridge, UK.
Hutchison
R E
RE
Hutchison
J B
JB
D000679:Amygdala / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism; D000728:Androgens / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D001141:Aromatase / Q000378:metabolism*; D047072:Aromatase Inhibitors; D001921:Brain / Q000033:anatomy & histology*; D001923:Brain Chemistry / Q000187:drug effects*; D004967:Estrogens / Q000494:pharmacology; D005260:Female; D007031:Hypothalamus / Q000201:enzymology; D007700:Kinetics; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D010053:Ovary / Q000201:enzymology; D011301:Preoptic Area / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism; D013739:Testosterone / Q000494:pharmacology
D000728:Androgens; D047072:Aromatase Inhibitors; D004967:Estrogens; D013739:Testosterone; D001141:Aromatase