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The enzyme cytochrome P450 aromatase is responsible for conversion of androgens to estrogens. Estrogens have been implicated in neurophysiology and neuropathology. The present study investigated the presence of aromatase immunoreactivity in the temporal, parietal and occipital cortices, olfactory bulb, cerebellum, and choroid plexus of the normal dog. Aromatase immunoreactivity was localized exclusively in neurons in the cortices and olfactory bulb. Immunoreactivity was also present in a small number of astrocytes in the substantia alba of the cerebellum. In the cortical regions, immunoreactive neurons, morphologically identified as pyramidal cells, were found throughout Layer II down to Layer VI, but not all pyramidal neurons were immunoreactive. In the olfactory bulb, immunoreactive neurons were mainly observed in mitral cells and inner granular cell layers. In the cerebellum, immunoreactivity was present in neurons of the deep cerebellar nuclei and in some neurons of the molecular and granular cell layers. Immunoreactivity was also present in endothelial cells of the subarachnoid vessels and those adjacent to ventricles in the cortex. The presence of well defined cytoplasmic aromatase immunoreactivity in neurons, some astrocytes, and endothelial cells suggests estrogen involvement in CNS physiology and function in the dog. The presence of aromatase in ependymal cells lining cerebral ventricles and choroid epithelial cells suggests that these cells may be partially responsible for estrogen concentration in the cerebrospinal fluid.
Content available remote Modulatory effect of ghrelin in prepubertal porcine ovarian follicles
Ghrelin is a novel growth hormone-releasing peptide, originally identified in rat stomach as an endogenous ligand of the growth hormone secretagogue receptor. Ghrelin is an important regulator of growth hormone secretion, food intake, and reproductive function. This study investigates whether or not ghrelin can modulate prepubertal pig ovary function, which was measured as ovarian estradiol secretion, aromatase activity, cell proliferation, and apoptosis. To investigate this, ovarian cells were co-cultured with four different doses of ghrelin (100, 250, 500, and 1000 pg/ml) for 48 h. Culture media samples were collected, and estradiol levels were determined, while aromatase expression was measured in the cultured cells. Cell apoptosis was measured by determination of caspase-3 activity, DNA fragmentation and TUNEL assay. Ghrelin in 250 and 500 pg/ml doses stimulated estradiol secretion. At all doses ghrelin stimulated aromatase activity and protein expression. Moreover, ghrelin increased cell proliferation and decreased apoptosis. This study provides novel evidence that ghrelin has a modulatory effect in the ovary. We suggest two mechanisms that explain how ghrelin acts on estradiol secretion: 1) ghrelin directly influences aromatase activity and protein expression; 2) ghrelin stimulates cell proliferation and antiapoptotic actions.
We evaluated impact of DDT isomers, o, p'- DDT [1, 1-dichloro-2, 2-bis (p, p'-chlorophenyl) ethylene] and p, p'-DDT [1, 1, 1-trichloro-2, 2-bis (p-chlorophenyl) ethane], and their metabolites, o, p'-DDE and p, p'-DDE, on ovarian steroidogenesis. All these compounds, except for p, p'-DDT, demonstrated estrogenic effects on steroid secretion in co-cultures of porcine prepubertal granulosa and theca cells. p,p'-DDT decreased progesterone and estradiol release, which was reversed by the addition of testosterone. In contrast, o, p'-DDT inhibited progesterone secretion with parallel stimulation of basal and testosterone-stimulated estradiol release. DDEs stimulated progesterone and estradiol secretion. The fluorometric assay confirmed that p,p'-DDE, o,p'-DDT, and o,p'-DDE stimulated aromatase activity. Western blots indicated that o,p-DDT and o,p'-DDE diminished the expression of estrogen receptor ß (ERß). This study demonstrated the isomer-dependent action of DDT in pig ovarian cells. We propose that DDT could disrupt ovarian steroidogenesis either by interfering with main steroidogenic enzymes or affecting ERß.
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