Localization of leptin receptor-like immunoreactivity in the corticotropes, somatotropes, and gonadotropes in the ovine anterior pituitary.
Leptin is a secreted product of the adipocytes that regulates a variety of functions. The presence of the leptin receptor (LR) has been demonstrated in the endocrine and neuroendocrine tissue, but only limited information is available regarding cell-specific expression in the anterior pituitary gland. We have used double-label immunofluorescence histochemistry to study the distribution of LR-like immunoreactivity (LR-ir) in the corticotropes, somatotropes, and gonadotropes of the ovine anterior pituitary. LR-ir was found in 34% of cells in the pars distalis and 94% of the cells in the pars tuberalis. In the pars distalis, LR-ir was present in 27% of corticotropes, 69% of somatotropes, and 29% of gonadotropes. In contrast, 90% of the gonadotropes in the pars tuberalis were immunopositive for LR. There was no alteration in the number of gonadotropes containing LR-ir during the various phases of the estrous cycle (n = 3/group) in the pars distalis (luteal phase, 36%; follicular phase, 32%; and estrous phase, 32%). In conclusion, we show that, in the pars distalis, LR-ir is expressed to a greater extent in the somatotropes than in the gonadotropes or corticotropes. This is in accordance with the documented effects of leptin on pituitary GH secretion. The differential expression of LR-ir between the gonadotropes of the pars distalis and pars tuberalis probably reflects the different phenotypes of the cells in these two regions. Lower levels of LR-ir expression in gonadotropes and corticotropes of the pars distalis may suggest that leptin does not substantially influence these particular cells, at least in this species.
Iqbal
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Prince Henry's Institute of Medical Research, Clayton, Victoria, Australia.
Pompolo
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Considine
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Clarke
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D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D004971:Estrus / Q000378:metabolism; D005260:Female; D013006:Growth Hormone / Q000378:metabolism*; D066298:In Vitro Techniques; D007986:Luteinizing Hormone / Q000378:metabolism*; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism*; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin; D012756:Sheep; D014018:Tissue Distribution
D002352:Carrier Proteins; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin; D000324:Adrenocorticotropic Hormone; D007986:Luteinizing Hormone; D013006:Growth Hormone