ISSN:
1365-2826
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
The aim of our study was to determine whether free α of glycoprotein hormones (free α) plays a role in lactotroph function during early pituitary development in the sheep foetus. Detection and quantification of free α, luteinzing hormone β-subunit (LHβ) and prolactin immunolabelling were determined by immunocytochemistry at days 32, 37, 42, 50 and 63 of gestation. Free α- and LHβ-containing cells were first detected in the ovine foetal pituitary gland on day 37 of gestation, while prolactin-containing cells were first identified on day 42. Analysis of serial sections suggested that free α immunoreactive cells were also LHβ-positive, indicating that free α was mainly synthesized by gonadotrophs. In early foetal stages, free α occurred in the antero-medio ventral region of the pituitary gland, whereas prolactin-containing cells were more dorsally and more caudally localized. The free α-, LHβ- and prolactin-immunostained area increased markedly between days 50 and 63 of gestation. To evaluate a possible functional relationship between gonadotrophs and lactotrophs, the effects of free α or gonadotropin releasing hormone (GnRH) on prolactin release were assayed. Chronic treatment of pituitary explants from male and female 42-day-old ovine foetuses for 8 days with 10−9 or 10−7 M ovine free α did not affect prolactin release. By contrast, free α administration on pituitary explants from male and female 50-day-old foetuses resulted in enhanced prolactin release. At this age, a daily (2 h per day) treatment with 10−8 M GnRH had similar stimulatory effect to free α whereas a ‘first day’ treatment (24 h on the first day) reduced prolactin release throughout the culture in males and had no effect in females. These results indicate that, despite early detection of free α at day 37 in the ovine foetal pituitary, its stimulatory effect on prolactin release occurs from day 50 of gestation, corresponding to the first period of lactotroph development in vivo. A daily treatment with GnRH mimics the effect of free α on prolactin release.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-2826.2001.00614.x
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