Immunohistochemical detection of growth hormone-releasing factor in brain

Abstract

The concept of a hypothalamic neurohumoral control for anterior pituitary secretion postulates the existence of a growth hormone-releasing factor (GRF) of neuronal origin that stimulates the pituitary gland to release growth hormone (GH). Such a compound has not yet been isolated and characterized from the brain, although there is extensive physiological and biochemical evidence for its existence (reviewed in ref. 2). However, a 44-amino-acid amidated peptide having the physiological properties of GRF as well as chemical similarities was recently isolated from a human pancreatic tumour that had caused acromegaly. Two shorter biologically active fragments of 40 and 37 residues were also isolated. The synthetic replicates of these human pancreas GRF (hpGRF) peptides specifically stimulate GH release in vitro and in vivo. Assuming similarity or identity between the putative hypothalamic GRF and the tumour-derived hpGRF, we have used immunohistochemistry to search for hpGRF-like immunoreactivity in the brain. We report here that antisera against the hpGRF1-40 peptide specifically stain neuronal cell bodies in the arcuate nucleus of the primate hypothalamus, with fibres projecting to the median eminence and ending in contact with portal vessels. This topography is characteristic of a neuronal system elaborating a releasing factor. These results provide evidence that hypothalamic GRF is very similar, if not identical, to hpGRF.

Novel Neuronal Phenotypes from Neural Progenitor Cells

“…An example of the absence of Category II staining in the hippocampus in general, and of TH neurons specifically, can be found in Figure 2. GRH GRH neurons increase growth hormone secretion and are centered in the lateral parts of the ARH (Bloch et al, 1983;Sawchenko et al, 1985) (Fig. 5).…”

Combined Autoradiographic and Immunohistochemical Evidence for an Association of Somatostatin Binding Sites with Growth Hormone‐Releasing Factor‐Containing Nerve Cell Bodies in the Rat Arcuate Nucleus

“…The net result is a striking ultradian rhythm of G H secretion (6). GRF-containing projections to the median eminence originate almost exclusively from nerve cell bodies located in the arcuate nucleus of the hypothalamus (7,8). In contrast, infundibular SRIF-containing axons have been shown to arise from neurons scattered along the lateral wall of the third ventricle in the anterior periventricular nucleus of the hypothalamus (9) from where they reach the median eminence via a lateral arc (10).…”

Discovery of growth hormone-releasing hormones and receptors in nonmammalian vertebrates

“…Thereafter, the sequences of GHRHs were determined in various vertebrate species and in protochordates (4). In mammals, GHRH is mainly expressed and released from the arcuate nucleus of the hypothalamus (5). The primary function of GHRH is to stimulate GH synthesis and secretion from anterior pituitary somatotrophs via specific interaction with its receptor, GHRH-R (5).…”