Carboxyl Ester Lipase (CEL) Expression in Normal Pituitary Gland and Pituitary Adenomas. Possible Role in the Modulation of Hormone Secretion Via Ceramide Pathway
S La Rosa, C Placidi, S Uccella, G Finzi, D Vigetti, M Losa, C Capella. Ospedale di Circolo, Varese, Italy; University of Insubria, Varese, Italy; Istituto Scientifico San Raffaele, Milan, Italy
Background: CEL is an enzyme secreted by acinar cells of the pancreas, which hydrolyzes a wide variety of lipid substrates. It has also been identified in other tissues including lactating mammary gland, endothelial cells and liver. Recent findings have demonstrated a role of CEL in the regulation of ceramide functions through inactivation by hydrolysis. Ceramides are lipid second messengers with several biological roles. They are also known to be involved in the regulation of pituitary hormone secretion and particularly in the inhibition of GH release in experimental models. However, there are no studies about the expression of CEL in normal human pituitary and in pituitary adenomas. The expression of CEL in normal and adenomatous pituitary cells may have a regulation role on hormone secretion.
Design: CEL expression was investigated in 10 normal pituitary glands and 86 well characterized (12 FSH/LH, 18 a-SU/null cell, 6 TSH, 21 ACTH, 11 PRL, and 18 GH) adenomas using immunohistochemistry, western blotting, RT-PCR and electron microscopy immunocytochemistry.
Results: In normal adenohypophysis CEL was localized in TSH and ACTH cells, while among adenomas it was mainly found in functioning ACTH, GH, and TSH tumors, while its expression was poor in the corresponding silent adenomas and was lacking in FSH/LH-cell, null-cell and prolactin-cell adenomas. Ultrastructurally, CEL was localized in secretory granules, close to their membranes.
Conclusions: This is the first study demonstrating CEL expression in human normal pituitary gland and in functioning GH, ACTH and TSH adenomas. Considering that CEL hydrolizes ceramides inactivating their inhibitory function on pituitary hormone secretion, our findings suggest a possible role of CEL in the regulation of hormone secretion in both normal and adenomatous pituitary cells.
Tuesday, March 23, 2010 1:00 PM
Poster Session IV # 52, Tuesday Afternoon