TY - JOUR
T1 - Regulation of gonadotropin-releasing hormone (GnRH)-receptor gene expression in tilapia
T2 - Effect of GnRH and dopamine
AU - Levavi-Sivan, Berta
AU - Safarian, Helena
AU - Rosenfeld, Hanna
AU - Elizur, Abigail
AU - Avitan, Ayelet
PY - 2004/6
Y1 - 2004/6
N2 - The present work was designed to study certain aspects of the endocrine regulation of gonadotropin-releasing hormone receptor (GnRH-R) in the pituitary of the teleost fish tilapia. A GnRH-R was cloned from the pituitary of hybrid tilapia (ta-GnRH-R) and was identified as a typical seven-transmembrane receptor. Northern blot analysis revealed a single GnRH-R transcript in the pituitary of approximately 2.3 kilobases. The ta-GnRH-R mRNA levels were significantly higher in females than in males. Injection of the salmon GnRH analog (sGnRHa; 5-50 μg/kg) increased the steady-state levels of taGnRH-R mRNA, with the highest response recorded at 25 μg/kg and at 36 h. At the higher dose of sGnRHa (50 μ/kg), taGnRH-R transcript appeared to be down-regulated. Exposure of tilapia pituitary cells in culture to graded doses (0.1-100 nM) of seabream (sbGnRH = GnRH I), chicken II (cGnRH II), or salmon GnRH (sGnRH = GnRH III) resulted in a significant increase in taGnRH-R mRNA levels. The highest levels of both LH release and taGnRH-R mRNA levels were recorded after exposure to cGnRH II and the lowest after exposure to sbGnRH. The dopamine-agonist quinpirole suppressed LH release and mRNA levels of taGnRH-R, indicating an inhibitory effect on GnRH-R synthesis. Collectively, these data provide evidence that GnRH in tilapia can up-regulate, whereas dopamine down-regulates, taGnRH-R mRNA levels.
AB - The present work was designed to study certain aspects of the endocrine regulation of gonadotropin-releasing hormone receptor (GnRH-R) in the pituitary of the teleost fish tilapia. A GnRH-R was cloned from the pituitary of hybrid tilapia (ta-GnRH-R) and was identified as a typical seven-transmembrane receptor. Northern blot analysis revealed a single GnRH-R transcript in the pituitary of approximately 2.3 kilobases. The ta-GnRH-R mRNA levels were significantly higher in females than in males. Injection of the salmon GnRH analog (sGnRHa; 5-50 μg/kg) increased the steady-state levels of taGnRH-R mRNA, with the highest response recorded at 25 μg/kg and at 36 h. At the higher dose of sGnRHa (50 μ/kg), taGnRH-R transcript appeared to be down-regulated. Exposure of tilapia pituitary cells in culture to graded doses (0.1-100 nM) of seabream (sbGnRH = GnRH I), chicken II (cGnRH II), or salmon GnRH (sGnRH = GnRH III) resulted in a significant increase in taGnRH-R mRNA levels. The highest levels of both LH release and taGnRH-R mRNA levels were recorded after exposure to cGnRH II and the lowest after exposure to sbGnRH. The dopamine-agonist quinpirole suppressed LH release and mRNA levels of taGnRH-R, indicating an inhibitory effect on GnRH-R synthesis. Collectively, these data provide evidence that GnRH in tilapia can up-regulate, whereas dopamine down-regulates, taGnRH-R mRNA levels.
KW - Dopamine
KW - Gonadotropin-releasing hormone receptor
KW - Onadotropin-releasing hormone
KW - Pituitary
UR - http://www.scopus.com/inward/record.url?scp=2642564476&partnerID=8YFLogxK
U2 - 10.1095/biolreprod.103.021998
DO - 10.1095/biolreprod.103.021998
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C2 - 14749295
AN - SCOPUS:2642564476
SN - 0006-3363
VL - 70
SP - 1545
EP - 1551
JO - Biology of Reproduction
JF - Biology of Reproduction
IS - 6
ER -
