Aromatase activity in cultured brain cells: difference between neurons and glia

At the level of the central nervous system (CNS) of several mammalian and non-mammalian species, estrogens may be intracellularly formed from circulating androgens through the action of the aromatase complex. Estrogenic steroids play a crucial role in organizing and directing certain behavioral and neuroendocrine responses both during the fetal/neonatal life and in adulthood. Biochemical and immunocytochemical studies have shown that the aromatase is particularly concentrated in CNS areas involved in the control of reproductive functions, such as the hypothalamus, the preoptic area and the limbic system; despite this large body of evidence, the exact cellular localization of this enzymatic complex within the different cell populations of the brain is still uncertain. In the experiments described here, the presence of the aromatase has been evaluated in the two main cellular components of the brain: the neurons and the glia. In these experiments, cultures of neurons obtained from the brains of 14-15-day-old rat embryos, mixed glial cells from 1-day-old rats and type 1 astrocytes derived from cultured glial cells, have been utilized. The aromatase has been also evaluated in oligodendrocytes isolated from adult male rat brain by density gradient ultracentrifugation. The aromatase activity has been assayed by an 'in vitro' radiometric method which quantifies the production of tritiated water from [1 beta-3H]-androstenedione as an index of estrogen formation. The validity of the method has been verified both on the placental microsomes and on rat hypothalamic tissue, in which the actual formation of estrogens has also been measured.(ABSTRACT TRUNCATED AT 250 WORDS)