Pituitary hormones and prolactin-releasing activity in rats with primary estrogen-induced pituitary tumors.

Abstract

Pituitary tumors were induced in Wistar-strain female rats by repeated injections of depot estradiol preparations. Fifty-five, 130, and 200 days after the last injection, eight or nine experimental animals and the same number of untreated control animals were sacrificed. Pituitary weight, histology, and content of DNA, PRL, GH, TSH, and LH, hypothalamic content of PRL-releasing activity (PRL-RA) and immunoreactive TRH, and serum levels of PRL, GH, TSH, LH, T3, T4, and estradiol were determined. The pituitaries in the estrogen-treated rats increased markedly in weight and DNA content, and formed tumors. There was a striking increase in serum levels of PRL and a less marked increase in PRL content of the pituitary. Hypothalamic PRL-RA was higher than in the controls 55 and 200 days after the last estrogen injection at a time when serum estradiol levels were similar to those of controls. On the other hand, TSH, LH, and, to a slight degree, GH were suppressed. Short term administration of estrogen resulted in...