Time- and dose-related effects of gonadotropin-releasing hormone on growth hormone and gonadotropin subunit gene expression in the goldfish pituitary.
The goldfish brain contains two molecular forms of gonadotropin-releasing hormone (GnRH): salmon GnRH (sGnRH) and chicken GnRH-II (cGnRH-II). In a preliminary report, we demonstrated the stimulation of gonadotropin hormone (GtH) subunit and growth hormone (GH) mRNA levels by a single dose of GnRH at a single time point in the goldfish pituitary. Here we extend the work and demonstrate time- and dose-related effects of sGnRH and cGnRH-II on GtH subunit and GH gene expression in vivo and in vitro. The present study demonstrates important differences between the time- and dose-related effects of sGnRH and cGnRH-II on GtH subunit and GH mRNA levels. Using primary cultures of dispersed pituitary cells, the minimal effective dose of cGnRH-II required to stimulate GtH subunit mRNA levels was found to be 10-fold lower than that of sGnRH. In addition, the magnitudes of the increases in GtH subunit and GH mRNA levels stimulated by cGnRH-II were found to be higher than the sGnRH-induced responses. However, no significant difference was observed between sGnRH and cGnRH-II-induced responses in vivo. Time-related studies also revealed significant differences between sGnRH- and cGnRH-II-induced production of GtH subunit and GH mRNA in the goldfish pituitary. In general, the present study provides novel information on time- and dose-related effects of sGnRH and cGnRH-II on GtH subunit and GH mRNA levels and provides a framework for further investigation of GnRH mechanisms of action in the goldfish pituitary.
Klausen
Christian
C
Department of Biological Sciences, University of Calgary, AB, Canada.
Chang
John P
JP
Habibi
Hamid R
HR
D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000502:physiology; D006054:Goldfish; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D006062:Gonadotropins / Q000096:biosynthesis* / Q000235:genetics; D013006:Growth Hormone / Q000096:biosynthesis* / Q000235:genetics; D008297:Male; D010902:Pituitary Gland / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D021122:Protein Subunits / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D013997:Time Factors
D006062:Gonadotropins; D021122:Protein Subunits; D012333:RNA, Messenger; D007987:Gonadotropin-Releasing Hormone; D013006:Growth Hormone