Localization of endothelin A receptors in the rat pituitary TSH cells: light- and electron-microscopic immunohistochemical studies.
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.
Furuya
S
S
National Institute for Physiological Sciences, Myodaiji, Okazaki, Japan. sonoko@nips.ac.jp
Hiroe
T
T
Ozaki
T
T
Takimoto
M
M
Hori
S
S
D000324:Adrenocorticotropic Hormone / Q000032:analysis; D000818:Animals; D000906:Antibodies; D000918:Antibody Specificity; D016466:CHO Cells; D002462:Cell Membrane / Q000648:ultrastructure; D006224:Cricetinae; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D007986:Luteinizing Hormone / Q000032:analysis; D016253:Microscopy, Immunoelectron / Q000379:methods; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000502:physiology*; D051381:Rats; D011922:Rats, Mutant Strains; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin / Q000032:analysis* / Q000235:genetics; D011994:Recombinant Proteins / Q000032:analysis; D017384:Sequence Deletion; D013972:Thyrotropin / Q000032:analysis*
D000906:Antibodies; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin; D011994:Recombinant Proteins; D000324:Adrenocorticotropic Hormone; D007986:Luteinizing Hormone; D013972:Thyrotropin