Divergent expression patterns of pituitary gonadotropin subunit and GnRH receptor genes to continuous GnRH in vitro and in vivo

Abstract

Continuous, as opposed to pulsatile, delivery of hypothalamic gonadotropin-releasing hormone (GnRH) leads to a marked decrease in secretion of pituitary gonadotropins LH and FSH and impairment of reproductive function. Here we studied the expression profile of gonadotropin subunit and GnRH receptor genes in rat pituitary in vitro and in vivo to clarify their expression profiles in the absence and continuous presence of GnRH. Culturing of pituitary cells in GnRH-free conditions downregulated Fshb, Cga, and Gnrhr expression, whereas continuous treatment with GnRH agonists upregulated Cga expression progressively and Gnrhr and Fshb expression transiently, accompanied by a prolonged blockade of Fshb but not Gnrhr expression. In contrast, Lhb expression was relatively insensitive to loss of endogenous GnRH and continuous treatment with GnRH, probably reflecting the status of Egr1 and Nr5a1 expression. Similar patterns of responses were observed in vivo after administration of a GnRH agonist. However, continuous treatment with GnRH stimulated LH secretion in vitro and in vivo, leading to decrease in LH cell content despite high basal Lhb expression. These data suggest that blockade of Fshb expression and depletion of the LH secretory pool are two major factors accounting for weakening of the gonadotroph secretory function during continuous GnRH treatment.

The sex-specific patterns of changes in hypothalamic-pituitary-gonadal axis during experimental autoimmune encephalomyelitis

“…For example, it is well established that the expression of Cga and Gnrhr, but not Lhb (Janjic et al, 2019), as well as LH secretion (Stojilkovic et al, 1994) depend on GnRH concentrations and pattern of application. Therefore, the downregulation in Cga and Gnrhr expression in anterior pituitary and the decrease in basal serum LH levels also indicate an altered GnRH secretion.…”

“…The probes and primers are listed in Table 1 and Table 2, respectively. The expression levels of target genes were quantified by comparative 2 -∆Ct method, using glyceraldehyde 3-phosphate dehydrogenase gene (Gapdh) as a reference gene, which was recently shown to be valid reference gene for pituitary tissues and cultured pituitary cells (Janjic et al, 2019).…”

“…We next examined the expression of Gnrhr, because GnRHR conveys GnRH actions on LH secretion; the expression of this gene is very tightly regulated by GnRH itself (Janjic et al, 2019). During EAE, both males and females showed a significant decrease in the expression of Gnrhr.…”

Brain and Pituitary Transcriptome Analyses Reveal the Differential Regulation of Reproduction-Related LncRNAs and mRNAs in Cynoglossus semilaevis

“…As shown in Figure 8 , the GnRHR, which belongs to the 7 transmembrane domain-containing class A superfamily of G-protein-coupled receptors (GPCRs), binds to G q/11 proteins to activate phospholipase C (PLC), which conveys its signal to diacylglycerol (DAG) and inositol 1,4,5-trisphosphate (IP3) ( Chang and Pemberton, 2018 ; Janjic et al, 2019 ). In this study, we found that members of the GPCR family, including GPCR family C group 5 member C (Gprc5c) GPR52 , and GPR4 , were significantly differentially expressed in the pituitary at ovarian stages V vs. VI.…”

Calcium-Prolactin Secretion Coupling in Rat Pituitary Lactotrophs Is Controlled by PI4-Kinase Alpha

“…qRT-PCR was performed in the presence of cDNA (2 ng), TaqMan™ Fast Advanced Master Mix, and TaqMan Gene Expression Assays using the Quantum Studio 6 Flex Real Time PCR System. Target gene expression levels were determined by the comparative 2^-(delta Ct) quantification method using Gapdh as the reference gene, which was previously established to be suitable for anterior pituitary tissue ( 36 ). Applied Biosystems pre-designed TaqMan Gene Expression Assays were used: prolactin ( Prl , 00561791_m1) and glyceraldehyde 3-phosphate dehydrogenase gene ( Gapdh ; Rn01462662_g1).…”