Gene expression and secretion of LH and FSH in relation to gene expression of GnRH receptors in the brushtail possum (Trichosurus vulpecula) demonstrates highly conserved mechanisms

Abstract

In eutherian mammals, the gonadotrophins (LH and FSH) are synthesized and stored in gonadotroph cells under the regulation of multiple mechanisms including GnRH. Very little is known about the regulation of gonadotrophin secretion and storage in pituitary glands of marsupials. This study revealed, using quantitative PCR and heterologous RIA techniques, that LHB mRNA expression levels remained constant over the oestrous cycle, regardless of the presence of a preovulatory LH surge, which is characteristic of a hormone secreted under regulation. Our sampling regime was unable to detect pulses of LH during the follicular phase, although GNRHR mRNA levels had increased at this time. Pulses of LH were, however, detected in the luteal phase of cycling females, in anoestrus females and in males. There was a positive correlation between gene expression of FSHB and plasma levels of FSH at different stages of the oestrous cycle and no pulses of FSH were detected at any time; all characteristics of a hormone secreted via the constitutive pathway. Using in situ hybridisation and immunohistochemistry methods, we determined that mRNA expression of LHB and FSHB, and protein storage of gonadotrophins exhibited a similar pattern of localisation within the pituitary gland. Additionally, sexual dimorphism of gonadotroph populations was evident. In summary, these findings are similar to that reported in eutherians and considering that marsupial evolution diverged from eutherians over 100 million years ago suggests that the regulation of gonadotrophins is highly conserved indeed.

GnRHa active immunity regulates expression of LHR protein and development of uteri in ewes

“…FSH and LH are synthesised and stored in the gonadotropin cells under the regulation of multiple mechanisms of GnRH and its agonists (Crawford et al 2009). LH binds to its receptor (LHR) in the somatic Sertoli cells and stimulates the production and secretion of abundant proteins.…”

“…However, the quantitative effects of GnRHa (especially alarelin acetate) immunity in the uterine development of ewes at different doses and durations still remain unclear (Chia et al 2006). It is indeterminate whether a GnRH agonist influences the expression level of LHR protein in the uterus of ewes (Crawford et al 2009). …”

Cloprostenol and eCG influence oestrus synchronisation and uterine development in mice

“…FSH and LH are synthesised and stored in gonadotrophin cells under the regulation of multiple mechanisms (Crawford et al 2009). In this study, serum LH and FSH concentrations in eCG and CLO mice increased following the cloprostenol and eCG injections.…”

Cloprostenol and pregnant mare serum gonadotropin promote estrus synchronization, uterine development, and follicle-stimulating hormone receptor expression in mice

“…Moreover, it also induces uterine contractions due to ecbolic properties, and it has an ovulatory effect, which is due to the immediate rise in gonadotropins (Friedman et al, 1991). Cloprostenol (CLO) is a potent prostaglandin (PGF) F2α analogue that influences the estrus of animals by lysing appearance of the corpus lutein (Crawford et al, 2009). The intraperitoneal administration of CLO three days apart may induce the appearance of estrus in 80% of mice (Pallares and Gonzalez-Bulnes, 2009).…”

“…Although mice are laboratory animals widely used for research worldwide, research on the management of the estrus cycle in mice is scarce (Marcondes et al, 2002;Crawford et al, 2009;Alejandro et al, 2012). The usual methods for the induction of behavioral estrus and ovulation are the "male effect" by the introduction of a fertile or vasectomized male and the "Whitten effect," which utilizes exposure to male pheromones.…”