Immunoreactive cytochrome P-45017α in rat and guineapig gonads, adrenal glands and brain
in ReproductionSummary. The cytochrome P-45017α-hydroxylase, 17→20 lyase (P-45017α) is the key enzyme responsible for the biosynthesis of androgens in steroidogenic organs. Its cellular localization has been examined with an immunohistochemical technique.
In immature rat ovary, P-45017α was first detected in sparse interstitial cells on postnatal Day 8. The number of immunoreactive interstitial cells increased thereafter and the intensity of P-45017α staining in these cells was highest at 3 weeks of age. The intensity of staining then started to decline and was very faint at Day 35. From 6 weeks on, the distribution of immunoreactive P-45017α was of the adult type: it was detected exclusively in the thecal cells of the large antral, preovulatory, follicles. P-45017α was not detectable during pregnancy except on the day of parturition, when thecal cells were transiently immunoreactive. The staining had vanished 24 h after delivery.
Human chorionic gonadotrophin (hCG), injected into immature females on Days 24 to 26, induced P-45017α prematurely in thecal cells. When injected on Days 12 to 14 of pregnancy, hCG also induced P-45017α in the thecal cells surrounding the largest follicles, whereas the interstitial and luteal cells were not immunostained. The anti-progestin RU486, injected on Day 16 of pregnancy, reinstated P-45017α (and P-450scc) immunoreactivity in the thecal cells. Oestradiol selectively suppressed P-45017α expression in the thecal cells of RU486-treated females.
In immature guinea-pig ovary, P-45017α was immunostained in thecal cells, not in interstitial cells, although the interstitial cells expressed the △5-3β-hydroxysteroid dehydrogenase.
P-45017α was also immunolocalized in the Leydig cells of rat and guinea-pig testes, and in the guinea-pig adrenal cortex (zonae fasciculata and reticularis), but not in the rat adrenal cortex. P-45017α was not detectable in the brain of either rat or guinea-pig.
Keywords: cytochrome P-45017α; cytochrome P-450scc; △5-3β-hydroxysteroid dehydrogenase; immunohistochemistry; ovary; testis; adrenal cortex; brain; rat; guinea-pig
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