Ultrastructural investigation of spontaneous pituitary gonadotroph cell adenomas in aging Sprague-Dawley rats

Abstract

Gonadotroph cell adenomas of the pituitary are infrequent in human patients and are not invariably associated with altered gonadal function. To date, no animal model of this tumor type exists. Herein, we describe spontaneous gonadotroph cell adenomas in old male and female Sprague-Dawley rats by histology, immunocytology and electron microscopy.The material consisted of the pituitaries of 27 male and 38 female Sprague Dawley rats, all 26 months of age or older, removed at routine autopsy. Sections of formal in-fixed, paraffin-embedded tissue were stained with hematoxylin-phloxine-saffron (HPS), the PAS method and the Gordon-Sweet technique for the demonstration of reticulin fibers. For immunostaining, sections were exposed to anti-rat β-LH, anti-ratβ-TSH, anti-rat PRL, anti-rat GH and anti-rat ACTH 1-39. For electron microscopy, tissue was fixed in 2.5% glutaraldehyde, postfixed in 1% OsO4 and embedded in epoxy-resin. Tissue fixed in 10% formalin, embedded in epoxy resin without osmification, was used for immunoelectron microscopy.

Extralabel use of cabergoline in the treatment of a pituitary adenoma in a rat

“…Pituitary adenomas are a common clinical and necropsy finding in geriatric rats. [1][2][3][4][5][6][7][8] The percentage of affected rats varies depending on factors such as age and sex; these types of factors should be considered when comparing the results among studies. However, in Sprague-Dawley and Fisher strains of rats that were > 24 months old, prevalences of pituitary adenomas were reported as 85% and 83%, respectively.…”

“…For the rat of this report, the classification system used was based on results obtained from Sprague-Dawley rats in which immunocytochemical and ultrastructural correlations were performed. 4,9,14 Almost all known adenohypophysial hormones have been immunocytochemically identified. Prolactin-producing pituitary adenomas are the most common, followed by gonadotroph cell adenomas and immunonegative adenomas; mixed prolactin and growth hormone-producing adenomas also have been described 4,9,14 Two types of prolactin-producing pituitary adenomas are recognized in rats.…”

“…4,9,14 Almost all known adenohypophysial hormones have been immunocytochemically identified. Prolactin-producing pituitary adenomas are the most common, followed by gonadotroph cell adenomas and immunonegative adenomas; mixed prolactin and growth hormone-producing adenomas also have been described 4,9,14 Two types of prolactin-producing pituitary adenomas are recognized in rats. 4,9,14 The more common prolactin-producing pituitary adenoma is described as a sparsely granulated adenoma.…”

“…Two types of mixed prolactin and growth hormone-producing adenomas are described. 4,9,14 Monomorphous pituitary adenomas are composed of cells immunoreactive for both prolactin and growth hormone. In contrast, bimorphous pituitary adenomas have predominantly immunoreactive cells only for prolactin, but some cells contain both growth hormone and prolactin.…”