Z. Li et Gv. Shah, ESTROGEN ATTENUATES EXPRESSION OF CALCITONIN-LIKE IMMUNOREACTIVITY INTHE ANTERIOR-PITUITARY GLAND, Endocrine, 3(6), 1995, pp. 453-459
Estrogens increase prolactin (PRL) synthesis and release in rats and h
umans, whereas pituitary-derived calcitonin-like immunoreactive peptid
e (pit-CT) inhibits PRL gene expression and release. To test the hypot
hesis that estrogens stimulate lactotrophs by diminishing pit-CT expre
ssion, the present studies examined effects of ovariectomy (ovx) and e
stradiol (E2) administration on (1) pit-CT IR cell population; (2) pit
-CT IR content and (3) release of pit-CT IR by cultured anterior pitui
tary (AT) cells. Ability of anti-calcitonin immunoglobulins (anti-CT I
gG) to stimulate PRL release from cultured AP cells was also examined.
The results suggest that ovariectomy induced a large increase in pit-
CT IR cell population in the AP gland and E2-treatment dramatically re
versed this increase. Similar changes were observed in pit-CT IR conte
nt of AP extracts. Cultured AP cells from ovx rats released significan
tly higher amounts of pit-CT IR, and anti-CT IgG induced a significant
increase in basal PRL release. AP cells from E2-treated rats secreted
lower amounts of pit-CT IR and this was associated with significantly
higher PRL release. These results suggest that estrogens may stimulat
e lactotrophs, at least in part, by removing inhibitory influence of e
ndogenous pit-CT.