Journal article

Estradiol-17 beta Inhibits Gonadotropin-Releasing Hormone-Induced Ca2 in Gonadotropes to Regulate Negative Feedback on Luteinizing Hormone Release

Javed Iqbal, Olivier Latchoumanin, Ika P Sari, Richard J Lang, Harold A Coleman, Helena C Parkington, Iain J Clarke

ENDOCRINOLOGY | ENDOCRINE SOC | Published : 2009

Abstract

In pituitary gonadotropes, estrogens have biphasic actions to cause an initial negative feedback followed by a positive feedback on LH secretion, but the mechanisms involved are not clearly understood. To investigate the feedback effects of estrogen, we used mixed ovine pituitary cell cultures (48-72 h), which were treated with 10(-9) M estradiol-17beta (E(2)) or vehicle followed by a pulse of 10(-9) M GnRH. Medium was collected for LH assay and cells extracted to determine activation of MAPK (phosphorylated ERK-1/2). E(2) treatment for 5 min reduced GnRH-induced LH release and caused phosphorylation of ERK-1/2. E(2) alone also caused phosphorylation of ERK-1/2, similar to the response evoke..

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