EFFECT OF ESTROGEN ON THE EXPRESSION OF GALANIN MESSENGER-RNA IN PITUITARY TUMOR-SENSITIVE AND TUMOR-RESISTANT RAT STRAINS

The hypothesis that estrogen-induced pituitary tumors are mediated by the neuropeptide galanin was tested using tumor-resistant (Sprague-Daw ley; SD) and tumor-sensitive (Fischer 344; F344) rat strains. Diethyls tilbestrol (DES) increased expression of galanin mRNA in both strains after 1, 2, and 4 weeks of treatment and doubled pituitary weights in F344 rats while pituitary weights in SD rats were unchanged by DES tre atment. In F344 rats, both the expression of galanin mRNA and pituitar y; weights increased linearly with the length of DES treatment. In SD rats however; despite increasing levels of galanin mRNA, pituitary wei ghts did not increase. These delta indicate that galanin gene expressi on, by itself is not sufficient to account for increased pituitary gro wth. However, our data do not rule out the possibility that galanin ha s an indirect role in promoting pituitary growth.