A comparison of aromatase, 5 alpha-, and 5 beta- reductase activities in the brain and pituitary of male and female quail (C. c. japonica).
In numerous vertebrate species including Japanese quail (Coturnix coturnix japonica), actions of testosterone (T) on neuroendocrine target tissues are mediated in part by conversion to estrogenic and androgenic metabolites. In order to assess which pathways were favored in each identified androgen target area in quail brain and whether there were discernible sex differences, we developed an assay for simultaneously quantifying aromatase, 5 alpha-, and 5 beta-reductase. In addition, we made the first definitive identification of aromatase in quail pituitary and compared all three enzyme activities in the pituitary of males and females. Enzymes were measured in tissue homogenates by the conversion of [3H]androstenedione to [3H]estrone, [3H]5 alpha-androstanedione, and 5 beta-androstanedione. Aromatase activity was restricted to limbic tissues (anterior hypothalamus greater than posterior hypothalamus greater than septum greater than archistriatum containing nucleus taenia) while hyperstriatum, cerebellum, and midbrain containing nucleus intercollicularis were aromatase-negative. Quail pituitary aromatized androgen at rates equivalent to anterior hypothalamus/pre-optic area (aHPOA). 5 alpha- and 5 beta-reductase were present in all tissues tested. Aromatase was significantly higher in aHPOA and pituitary of males, whereas 5 alpha-reductase was significantly higher in female pituitary. These data suggest that a complex of androgen-metabolizing enzymes controls the neuroanatomic (spatial) distribution of active hormone in neuroendocrine tissues and that quantitative differences between males and females may account for sex differences in behavior.
D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000378:metabolism; D000704:Analysis of Variance; D000818:Animals; D001141:Aromatase / Q000378:metabolism*; D001921:Brain / Q000201:enzymology*; D003370:Coturnix / Q000378:metabolism*; D005260:Female; D008297:Male; D010088:Oxidoreductases / Q000378:metabolism*; D010902:Pituitary Gland / Q000201:enzymology*; D011784:Quail / Q000378:metabolism*; D012737:Sex Factors
D010088:Oxidoreductases; D001141:Aromatase; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase; C021936:3-oxo-5 beta-steroid delta 4-dehydrogenase