ESTROGEN STIMULATION OF GALANIN GENE-EXPRESSION AND GALANIN-LIKE IMMUNOREACTIVITY IN THE RAT AND ITS BLOCKADE BY THE ESTROGEN ANTAGONIST KEOXIFENE (LY156758)

Rat galanin (rGAL) gene expression is stimulated potently by 17beta-estradiol in the anterior pituitary. Neuroendocrine tissue extracts of were purified by chromatography and analyzed for rGAL-like (-LI) immunoreactivity. Greater than 90% of rGAL-LI eluted at the same position as the synthetic rGAL standard in untreated anterior pituitary, median eminence and neurointermediate lobe tissues. Additional immunoreactive forms were detected in the hypothalamus, anterior pituitary and MtT/W 15 adenoma tissues, particularly after 17beta-estradiol treatment. We examined rGAL and its encoding mRNA in the anterior pituitary of immature female rats after the injection of pregnant mare serum gonadotropin (PMSG). One and two days after PMSG injection, serum 17beta-estradiol increased 3-fold and 4-fold, respectively. This resulted in a surge of endogenous gonadotropin 2 days after PMSG. At this time, rGAL-encoding mRNA was increased 40-fold over controls. Three days after PMSG, there was a 6-fold increase in anterior pituitary and a 41% increase in plasma rGAL-LI concentrations. Plasma 17beta-estradiol one day after injection of PMSG and the consequent anterior pituitary rGAL-LI concentrations 2 days later were positively correlated. This stimulation of rGAL and its encoding mRNA by PMSG was inhibited by treatment with the estrogen antagonist keoxifene (LY156758).