RESUMO
The present study examined the differential mRNA expression levels of three forms of GnRH (sGnRH, pjGnRH and cGnRH-II) and two forms of GnRH receptor (pjGnRH-R I and pjGnRH-R II) in the brain, pituitary, and ovaries of pejerrey in relation to the reproductive status. The analysis revealed the presence of significant amounts of mRNA of the three GnRH forms while the ovaries showed only two (sGnRH and pjGnRH). The GnRH receptor II was found ubiquitously in the brain, pituitary, and ovaries while the form I was detected only in the brain. The levels of pjGnRH mRNA in the brain and pjGnRH-R II in the pituitary gland varied in correlation with the ovarian condition. However, brain sGnRH and pjGnRH-R I mRNA levels reached a maximum during early stages of ovarian development. In contrast, the brain levels of cGnRH-II mRNA showed no variation. The present study also shows a good correlation of ovarian sGnRH and pjGnRH-R II mRNA levels with the reproductive condition, suggesting that these molecules are may be involved in the regulation of pejerrey ovarian function.
Assuntos
Encéfalo/metabolismo , Hormônio Liberador de Gonadotropina/genética , Oogênese/fisiologia , Ovário/metabolismo , Hipófise/metabolismo , Receptores LHRH/genética , Smegmamorpha/fisiologia , Animais , Feminino , Perfilação da Expressão Gênica , RNA Mensageiro/metabolismo , Reprodução/fisiologia , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Smegmamorpha/genética , Smegmamorpha/metabolismoRESUMO
About 50years after Harris's first demonstration of its existence, GnRH has strongly stimulated the interest and imagination of scientists, resulting in a high number of studies in an increasing number of species. For the endocrinologist, GnRH, via its actions on the synthesis and release of pituitary gonadotrophins, is first an essential hormone for the initiation and maintenance of the reproductive axis, but recent data suggest that GnRH emerged in animals lacking a pituitary. In this context, this review intends to explore the current status of knowledge on GnRH and GnRH receptors in metazoa in order to see if it is possible to draw an evolutive scenario according to which GnRH actions progressively evolved from the control of simple basic functions in early metazoa to an indirect mean of controlling gonadal activity in vertebrates through a sophisticated network of finely tuned neurons developing in a rather fascinating way. This review also intends to provide an evolutive scenario based on the recent advances of whole genome sequencing possibly explaining the number of GnRH and GnRH receptor variants according to the 2R and 3R theories accompanied by gene losses.
Assuntos
Evolução Biológica , Hormônio Liberador de Gonadotropina/fisiologia , Receptores LHRH/fisiologia , Animais , Hormônio Liberador de Gonadotropina/genética , Humanos , Modelos Biológicos , Modelos Neurológicos , Filogenia , Receptores LHRH/genética , Vertebrados/genéticaRESUMO
The second GnRH form, originally identified in chickens (cGnRH-II or GnRH-II), is the most ubiquitous peptide of the GnRH neuropeptide family, being present from jawed fish to human beings. However, the presence of GnRH-II in such an important experimental model as the rat is still an object of discussion. Here we present chromatographic, immunologic and biologic activity evidence supporting the expression of GnRH-II in the rat. Olfactory bulb, hypothalamus, remnant brain and anterior pituitary from a pool of 50 female adult rats were extracted and subjected to RP-HPLC on a C-18 column. The fractions were collected and evaluated by using two different RIA systems, specific for GnRH-I and GnRH-II respectively. Under these conditions the GnRH-I standard eluted in fraction 21 (f21) was only detected with the GnRH-I RIA system, whereas the GnRH-II standard was only detected in the fraction 27 (f27) by using a GnRH-II RIA system. In the olfactory bulbs extract, the fractions analyzed by the GnRH-I RIA systems showed a single peak in f21, whereas by using the GnRH-II RIA system a single peak at f27 was observed. In the hypothalamus GnRH-I was detected in f21 meanwhile GnRH-II could not be detected. When the remnant brain and pituitary gland extracts were analyzed, both GnRH forms were detected. To the best of our knowledge, this is the first report concerning GnRH-II detection in a mammalian pituitary. Serial dilutions of f27 and GnRH-II presented similar displacement of radioiodinated-GnRH-II, demonstrating that both molecules share immunological properties. Moreover, after 60 min stimulation, both f27 and GnRH-II had similar LH and FSH releasing activity in 12 day-old rat pituitary primary cell cultures. However, we failed to characterize the GnRH-II gene in this model. These results provide strong evidence for the expression of GnRH-II in the rat brain and pituitary gland.
