INTRACELLULAR PARTITIONING OF ANDROGEN RECEPTOR IMMUNOREACTIVITY IN THE BRAIN OF THE MALE SYRIAN-HAMSTER - EFFECTS OF CASTRATION AND STEROID REPLACEMENT
Ri. Wood et Sw. Newman, INTRACELLULAR PARTITIONING OF ANDROGEN RECEPTOR IMMUNOREACTIVITY IN THE BRAIN OF THE MALE SYRIAN-HAMSTER - EFFECTS OF CASTRATION AND STEROID REPLACEMENT, Journal of neurobiology, 24(7), 1993, pp. 925-938
The effect of castration and steroid replacement on the intracellular
partitioning of the androgen receptor in the brain of the male Syrian
hamster was determined using immunocytochemistry. Androgen receptors w
ere visualized using the PG-21 antibody (G. S. Prins) on 40-mum corona
l brain sections from hamsters perfused with 4% paraformaldehyde with
or without 0.4% glutaraldehyde. Control studies confirmed antibody spe
cificity in gonad-intact and castrate males. In the normal adult male,
androgen receptor immunocytochemistry reveals intense staining confin
ed to the cell nucleus. Castration caused a gradual increase in cytopl
asmic labelling within 2 weeks, accompanied by a reduction in nuclear
staining intensity in androgen receptor-containing neurons throughout
the brain. Cytoplasmic androgen receptor staining was eliminated after
treatment of orchidectomized males for only 8 h with exogenous testos
terone. Likewise, long-term exposure to testosterone and dihydrotestos
terone, a nonaromatizable androgen, maintained nuclear androgen recept
or immunoreactivity. However, exposure to low physiologic concentratio
ns of estrogen was not effective in this regard. In addition, we deter
mined that nuclear androgen receptor immunoreactivity decreases in res
ponse to inhibitory short-day photoperiod, but without an increase in
cytoplasmic immunostaining. This appears to be due to the decrease in
androgen production by the testis, rather than a direct photoperiodic
effect, because testosterone supplementation to short-day males restor
ed the intensity of nuclear androgen receptor immunoreactivity to leve
ls comparable to those in the intact male. These findings are compatib
le with a new model for the intracellular localization of androgen rec
eptors, in which a subset of unoccupied receptors is located in the ce
ll cytoplasm in the absence of ligand. They further demonstrate the re
partitioning of such cytoplasmic receptors, thereby confirming and ext
ending previous observations using biochemical techniques on the regul
ation of neuronal androgen receptors.