The Ultrastructural Basis For Increased Prolactin Synthesis and Release From Anterior Pituitary Glands of Estrogen-Progesterone Primed Ovariectomized Rats: Correlated Electron Microscopy and Radioimmunoassay

In rats, physiological studies show that ovariectomy results in a reduced concentration of circulating prolactin. Conversely, ovariectomized rats given estrogen have elevated serum prolactin and increased amounts of prolactin in the anterior pituitary gland. Separate electron microscopic studies suggest modifications in fine structure of prolactin producing (LTH) cells based on relatively large cumulative amounts of estrogen given alone or with comparably high doses of progesterone to adult virgin female or ovariectomized rats. This study was undertaken to provide a correlated morphological and physiological investigation of LTH cells and prolactin levels in a model commonly used by many researchers. Six to seven weeks after bilateral ovariectomy, a group of adult female rats was primed by a subcutaneous injection of 50 ng of estradiol benzoate and 25 mg of progesterone.