Localization of endothelin A receptors in the rat pituitary TSH cells: light- and electron-microscopic immunohistochemical studies

• Published in: Cell and tissue research 2000-10, Vol.302 (1), p.85-94
• Main Authors: Furuya, S, Hiroe, T, Ozaki, T, Takimoto, M, Hori, S
• Format: Article
• Language: English
• Subjects: Adrenocorticotropic Hormone - analysis; Animals; Antibodies; Antibody Specificity; Cell Membrane - ultrastructure; CHO Cells; Cricetinae; Humans; Immunohistochemistry - methods; Luteinizing Hormone - analysis; Microscopy, Immunoelectron - methods; Pituitary Gland, Anterior - cytology; Pituitary Gland, Anterior - physiology; Rats; Rats, Mutant Strains; Receptor, Endothelin A; Receptor, Endothelin B; Receptors, Endothelin - analysis; Receptors, Endothelin - genetics; Recombinant Proteins - analysis; Sequence Deletion; Thyrotropin - analysis
• ISSN: 0302-766X; 1432-0878
• DOI: 10.1007/s004419900169

Endothelins modulate hormonal secretion in the pituitary gland. Intense signaling of endothelin A receptors (ET(A)R) has been detected by in situ hybridization, binding assay and receptor autoradiography. We used light- and electron-microscopic immunohistochemistry of ET(A)R with polyclonal antibody against a synthetic peptide corresponding to the carboxyl terminus (403-427) of human ET(A)R. Immunoreactivity was observed in 6-8% of anterior pituitary cells, which were rather large polygonal or stellate cells. These cells were often clustered. Double-staining immunofluorescence showed that the ET(A)R-positive cells immunoreacted with antibody against the beta-subunit of thyroid-stimulating hormone (TSH), but not adrenocorticotropic hormone (ACTH) or lutenizing hormone beta (LHbeta). Pre- and postembedding electron-microscopic immunohistochemistry showed that ET(A)R-positive cells had vacuolated or parallel-lined rough endoplasmic reticulum (rER) and numerous round granules in their periphery and the elongated processes. By pre-embedding immunohistochemistry, diaminobenzidine tetrahydrochloride (DAB) products were shown to be mostly located around the granules and occasionally underneath the plasma membrane. By postembedding immunohistochemistry, granules in the ET(A)R-positive cells were 90-150 nm in diameter, and colloidal gold particles due to ET(A)R were associated with about 10% of these granules. These results indicate that ET(A) receptors are associated mostly with the secretory granules of TSH cells.