ESTRADIOL STIMULATES GROWTH-HORMONE PRODUCTION IN FEMALE GOLDFISH

Citation
Jj. Zou et al., ESTRADIOL STIMULATES GROWTH-HORMONE PRODUCTION IN FEMALE GOLDFISH, General and comparative endocrinology, 106(1), 1997, pp. 102-112
Citations number
51
Categorie Soggetti
Endocrynology & Metabolism
ISSN journal
00166480
Volume
106
Issue
1
Year of publication
1997
Pages
102 - 112
Database
ISI
SICI code
0016-6480(1997)106:1<102:ESGPIF>2.0.ZU;2-J
Abstract
The effects of estradiol (E(2)) on growth hormone (GH) production was investigated in gonad-intact female goldfish. It was first necessary t o generate a specific antibody for use in immunocytochemistry, Western , and dot-blot analyses of GH production. To accomplish this, grass ca rp GH (gcGH) cDNA was cloned by the reverse transcription polymerase c hain reaction (RT-PCR) and expressed in Echerichia coli and a specific polyclonal antibody to recombinant gcGH was generated in the rabbit. In Western blot, the anti-gcGH antibody specifically immunoreacted wit h recombinant gcGH, purified natural common carp GH, and with a single 21.5-kDa GH form from pituitary extracts of grass carp, common carp, goldfish, and zebrafish but not salmon, trout, or tilapia. Intraperito neal injection of the recombinant gcGH enhanced the growth rates of ju venile common carp demonstrating biological activity of this GH prepar ation. Electron microscopic studies showed that the anti-gcGH-I antibo dy specifically reacted with GH localized in the secretory granules of the goldfish somatotroph. Using anti-gcGH-I in a dot-blot assay, it w as found that in vivo implantation of solid silastic pellets containin g E(2) (100 mu g/g body weight for 5 days) increased pituitary GH cont ent by 150% in female goldfish. In a second, independent study employi ng a previously characterized anticommon carp GH antibody for radioimm unoassay, it was found that E(2) increased pituitary GH content by 170 % and serum GH levels by approximately 350%. The E(2)-induced hypersec retion of GH and increase in pituitary GH levels was not associated wi th changes in steady-state pituitary GH mRNA levels, suggesting that t his sex steroid may enhance GH synthesis at the posttranscriptional or translational level. Previous observations indicate that GH can stimu late ovarian E(2) production. The present results show that E(2) can i n turn stimulate GH production, indicating the existence of a novel pi tuitary GH-ovarian feedback system in goldfish. (C) 1997 Academic Pres s.