Evidence of gonadotropin-releasing hormone mRNA in the rat anterior pituitary.

Abstract

We have previously reported the presence and the persistence of immunoreactive GnRH cells in the rat anterior pituitary in the absence of exogenous GnRH. To substantiate the hypothesis of its endogenous production, we have investigated the presence of GnRH mRNA in rat anterior pituitary tissue using a reverse transcription-polymerase chain reaction (RT-PCR) amplification protocol. Total RNA from rat anterior pituitary, hypothalamus (positive control), and muscle (negative control) was reverse transcribed to the first strand of cDNA and amplified by PCR using a set of three exon-specific primers for a target sequence of the GnRH gene, i.e. two external 5' and 3' primers and one internal 3' primer. UV light analysis of the size-fractionated RT-PCR products showed two bands of the predicted sizes [511 and 397 base pairs (bp)] hybridizing with GnRH probes in Southern analysis only in hypothalamus and in anterior pituitary but not in muscle. These two bands were far more intense in the hypothalamus than in the anterior pituitary. Restriction enzyme analysis evidenced that the two RT-PCR products included the HindIII endonuclease site of cleavage present in the GnRH cDNA sequence spanned by the primers, yielding two digested products of the anticipated sizes (86 and 425 bp for the 511-bp fragment, and 86 and 311 bp for the 397-bp fragment). The complementary sequences for the GnRH probes were conserved in the 425-bp and 311-bp fragments. Based on these results, we can conclude that the RT-PCR products generated from RNA tissue were the target GnRH sequences in the anterior pituitary as well as in the hypothalamus.(ABSTRACT TRUNCATED AT 250 WORDS)

Gonadotropin-Releasing Hormone and Gonadotropin-Releasing Hormone Receptor Messenger Ribonucleic Acids Expression in Nontumorous and Neoplastic Pituitaries1

“…In this study, both GnRH and GnRH-R mRNAs were detected in nontumorous pituitaries. Detection of GnRH-containing cells (12) and of GnRH mRNA in the rat anterior pituitary has been reported (13) and suggests that endogenously synthesized GnRH may be involved in local regulatory mechanisms.…”

“…The presence of GnRH-producing cells (11) and of GnRH messenger RNA (mRNA) (12) has been reported in rat anterior pituitary, which suggests that endogenously synthesized GnRH may be involved in local regulatory mechanisms. Alexander et al (13) detected GnRH-R mRNA in human pituitary adenomas in vitro.…”

Corticotropin-releasing hormone is produced by rat corticotropes and modulates ACTH secretion in a paracrine/autocrine fashion.

“…The anterior pituitary has been found to harbor, apart from classical adenohypophyseal hormones, several other peptides which participate in cell-tocell interactions and modulate hormonal secretion (2). In this context, the synthesis of hypothalamic releasing factors, such as thyrotropin-releasing hormone, growth hormone-releasing hormone, somatostatin, and gonadotropin-releasing hormone has been demonstrated recently in normal and tumoral anterior pituitaries (5,7,9,10,12). These factors exert direct effects on anterior pituitary hormone production and release as well as on cell differentiation and growth, via their receptors located on the pituicytes.…”

“…So far, conclusive evidence has been put forward for the synthesis and secretion of thyrotropin-releasing hormone (5,6), somatostatin (7,8), growth hormone-releasing hormone (8,9), gonadotropin-releasing hormone (10,11), and vasopressin (12,13) by normal anterior pituitary cells. As regards corticotropin-releasing hormone (CRH), 1 mRNA for this hormone has been found in the whole pituitary gland (14) but whether this signal derives from the adenohypophysis or the posterior pituitary, which cells are responsible for CRH gene expression, and whether locally produced CRH in fact modulates corticotrope secretion have not been established.…”

Thyrotropin-Releasing Hormone Gene Expression in Cultured Anterior Pituitary Cells: Role of Gender

“…Numerous neuropeptides, originally isolated from the hypothalamus based on their hypophysiotrophic activity, have now been located in normal and tumorous anterior pituitary (AP) tissue [1][2][3][4][5][6][7][8][9][10][11][12]. Dependent on the cell of ori gin, gonadal steroids have been implicated in the regula tion of some of these hypophysial neuropeptides [2, 13-lb].…”