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The gonadotropin‐releasing hormone family of neuropeptides in the brain of human, bovine and rat: identification of a third isoform
Author(s) -
Yahalom Dror,
Chen Alon,
Ben-Aroya Nurit,
Rahimipour Shai,
Kaganovsky Ella,
Okon Eli,
Fridkin Mati,
Koch Yitzhak
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)01638-5
Subject(s) - gene isoform , median eminence , hypothalamus , gonadotropin releasing hormone , endocrinology , radioimmunoassay , medicine , biology , anterior pituitary , hormone , luteinizing hormone , neuropeptide , gonadotropic cell , pituitary gland , arcuate nucleus , receptor , biochemistry , gene
The mammalian gonadotropin‐releasing hormone (GnRH‐I), which regulates reproduction, was the first isoform of GnRH that was identified in mammals. Recently, we and others have demonstrated the existence of a second isoform of GnRH in the brain of mammals. The presence of a third isoform of GnRH, GnRH‐III, in the brain of mammals is reported herein. GnRH‐III, extracted from the brain of bovine and human, was purified by high performance liquid chromatography, using two distinct elution programs. In both, GnRH‐III was eluted at the same positions as synthetic salmon GnRH, as demonstrated by radioimmunoassay. The luteinizing hormone‐releasing activity of purified GnRH‐III, using dispersed rat pituitary cells, was found to be similar to that of synthetic salmon GnRH. The total amount of GnRH‐III, determined by radioimmunoassay, in the hypothalamus and midbrain of humans and calves is similar to that of GnRH‐I. Immunohistochemical studies demonstrated GnRH‐III‐containing neurons in the hypothalamus and midbrain of human and GnRH‐III fibers in the median eminence of rats. The distribution of GnRH‐III in the brain suggests that in addition to a putative function as a neurohormone at the hypothalamic–pituitary axis, GnRH‐III may have other functions. Our present results suggest that multiple isoforms of GnRH are present in the brain of mammals, and further studies are required in order to elucidate their biological functions.