Temporal expression of G-protein-coupled receptor 54 (GPR54), gonadotropin-releasing hormones (GnRH), and dopamine receptor D2 (drd2) in pubertal female grey mullet, Mugil cephalus.
ABSTRACT The G-protein-coupled receptor 54 (muGPR54) cDNA was cloned from the brain of the grey mullet, and its expression level, as well as those of the gonadotropin-releasing hormones (GnRH1, GnRH2, GnRH3) and dopamine receptor D2 (drd2), in the brain, pituitary and ovary of pubertal fish (early, intermediate, advanced) were determined by real-time quantitative RT-PCR (QPCR). The muGPR54 cDNA has an open reading frame of 1140 bp with a predicted 380 amino acid peptide, containing seven putative transmembrane domains and putative N-glycosylation and protein kinase C phosphorylation sites. QPCR results showed that the early stage of puberty in grey mullet is characterized by significantly high levels of expression of GPR54, GnRH and drd2 in the brain relative to the intermediate and advanced stages, except for GnRH1 that increased at the advanced stage of puberty. In the pituitary, drd2 expression declined significantly at the advanced stage relative to levels at the intermediate stage. Ovarian expression of GPR54 significantly increased from the intermediate stage of puberty relative to the early stage while that of GnRH1 acutely increased at the advanced stage of puberty. The ovarian expression of drd2 decreased as puberty progressed, but the changes were not significant. The results suggest the possible role of GPR54 and GnRH in positively regulating pubertal development in grey mullet and the dopaminergic inhibition of reproductive function mediated by drd2.
Full-textDOI: · Available from: Berta Sivan, Nov 24, 2014
SourceAvailable from: Jose M. Guzman[Show abstract] [Hide abstract]
ABSTRACT: Efforts to establish sustainable and efficient aquaculture production of sablefish (Anoplopoma fimbria) have been constrained by delayed puberty in cultured females. This study integrates a series of experiments aimed at gaining an understanding of the reproductive physiology of puberty in female sablefish. We detected transcripts for the dopamine D2 receptor (drd2) in brain, pituitary and ovary of sablefish, and prepubertal females exhibited significantly elevated brain and pituitary drd2 expression relative to wild maturing females. Treatments with sustained-release cholesterol pellets containing testosterone (T) and the dopamine D2 receptor antagonist, metoclopramide (Met), stimulated expression of pituitary luteinizing hormone beta subunit (lhb) and follicle-stimulating hormone beta subunit (fshb), respectively, in prepubertal females, whereas a combination of T and gonadotropin-releasing hormone agonist (GnRHa) had a strong synergistic effect on lhb expression (2000-fold higher than control). Although T induced a significant increase in the maximum ovarian follicle volume, none of the treatments tested stimulated onset of vitellogenesis. Using liquid chromatography/tandem mass spectrometry, we demonstrated that Met stimulated production of T by previtellogenic ovarian follicles in vitro, whereas gonadotropin preparations enhanced 17α-hydroxyprogesterone, androstenedione (A4), T and 17β-estradiol (E2) production. Treatment with T increased production of A4, 11β-hydroxyandrostenedione, 11β-hydroxytestosterone, E2, 11-ketotestosterone, and 5α-dihydrotestosterone (DHT). Interestingly, in the presence of high doses of T the previtellogenic ovary preferentially produced A4 and DHT over any other metabolite. Our data suggest the existence of dopamine inhibition of the reproductive axis in female sablefish. Treatments with Met and T elevated gonadotropin mRNAs in prepubertal females but failed to stimulate the transition into vitellogenic growth, suggesting a possible failure in pituitary gonadotropin protein synthesis/release. Previtellogenic ovarian follicles of sablefish are equipped to synthesize steroids, including those required for the vitellogenic growth, and DHT a steroid hormone whose role in reproduction of fishes remains unknown. Copyright © 2015. Published by Elsevier Inc.General and Comparative Endocrinology 04/2015; DOI:10.1016/j.ygcen.2015.02.024 · 2.67 Impact Factor
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ABSTRACT: The aim of the experiments was to evaluate the influence of human kisspeptin on LH secretion of Prussian carp (Carassius gibelio) females during ovarian recrudescence and spawning season. For the experiments, human kisspeptin KISS1 (0.1 mg kg-1 of body weight – b.w.), GnRH analogue (Des Gly10, D-Ala6) GnRH-A (20 μg kg-1 b.w.) and dopamine antagonist (pimozide) (5 mg kg-1 b.w.) were used alone or in combinations. At 3, 6, 12, 24 hours after injection(s) blood samples were collected from all fish. LH levels were measured in plasma with the use of the ELISA method. KISS1 did not show any significant effects on spontaneous LH secretion in both tested seasons. At 12 hours sampling time (both stages of gonad maturity) a combination of tested compounds (GnRH-A+KISS1) significantly increased LH release in comparison with the control. In the stage of gonad recrudescence KISS1 significantly increased LH secretion evoked by pimozide at 24 hours. A combination of three components: KISS1, GnRH-A, and pimozide significantly decreased LH secretion in comparison to LH secretion evoked by GnRH-A and pimozide during stage of gonad recrudescence. These results suggest that kisspeptin is involved in seasonal control of reproduction in Prussian carp. The possible interaction of kisspeptin and the dopaminergic system is also discussed.Folia Biologica 02/2015; 63(1). DOI:10.3409/fb63_1.25 · 0.48 Impact Factor
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ABSTRACT: This study investigated possible involvement of photoperiodic regulation in reproductive endocrine system of female olive flounder. To investigate the influence on brain-pituitary axis in endocrine system by regulating photoperiod, compared expression level of Kisspeptin and sbGnRH mRNA in brain and FSH-β, LH-β and GH mRNA in pituitary before and after spawning. Photoperiod was treated natural photoperiod and long photoperiod (15L:9D) conditions from Aug. 2013 to Jun. 2014. Continuous long photoperiod treatment from Aug. (post-spawning phase) was inhibited gonadal development of female olive flounder. In natural photoperiod group, the Kiss2 expression level a significant declined in Mar. (spawning period). And also, FSH-β, LH-β and GH mRNA expression levels were increasing at this period. However, in long photoperiod group, hypothalamic Kiss2, FSH-β, LH-β and GH mRNA expression levels did not show any significant fluctuation. These results suggest that expression of hypothalamic Kiss2, GtH and GH in the pituitary would change in response to photoperiod and their possible involvement of photoperiodic regulation in reproductive endocrine system of the BPG axis.03/2015; 19(1):11-7. DOI:10.12717/devrep.2015.19.1.011