Insulin-like growth factor-I mRNA and peptide in the human anterior pituitary.
The pituitary is the central organ regulating virtually all endocrine processes, and pathologies of the pituitary cause manifold adverse effects. Because insulin-like growth factor (IGF)-I appears to be involved in tumour pathogenesis, progression, and persistence, and only few data exist on the cellular synthesis sites of IGF-I, the present study aims to create a basis for further research on pituitary adenomas by investigating the presence of IGF-I in the human pituitary using reverse transcriptase-polymerase chain reaction, in situ hybridisation, immunohistochemistry and immunocytochemistry. IGF-I was expressed in the pituitary, and gene sequence analysis revealed a sequence identical to that found in human liver. The distribution pattern of IGF-I mRNA found by in situ hybridisation corresponded to that of IGF-I peptide in immunohistochemistry. In all pituitary samples investigated, IGF-I-immunoreactivity occurred in almost all adrenocorticotrophic hormone (ACTH)-immunoreactive cells. Occasionally, an interindividually varying number of growth hormone (GH) and, infrequently, follicle-stimulating hormone and luteinising hormone cells contained IGF-I-immunoreactivity but none was detected in supporting cells. At the ultrastructural level, IGF-I-immunoreactivity was confined to secretory granules in coexistence with ACTH- or GH-immunoreactivity, respectively, indicating a concomitant release of the hormones. Thus, in humans, IGF-I appears to be a constituent in ACTH cells whereas its production in GH-producing and gonadotrophic cells may depend on the physiological status (e.g. serum IGF-I level, age or reproductive phase). It is assumed that locally produced IGF-I plays a crucial role in the regulation of endocrine cells by autocrine/paracrine mechanisms in addition to the endocrine route.
Jevdjovic
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Division of Neuroendocrinology, Institute of Anatomy, University of Zürich, Zürich, Switzerland.
Bernays
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RL
Eppler
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D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000328:Adult; D005260:Female; D013006:Growth Hormone / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014018:Tissue Distribution
D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D000324:Adrenocorticotropic Hormone; D013006:Growth Hormone