Influence of thyroidal status on ovarian function in rainbow trout,Salmo gairdneri

✍ Scribed by Cyr, Daniel G. ;Eales, J. G.

• Publisher: John Wiley and Sons
• Year: 1988
• Tongue: English
• Weight: 654 KB
• Volume: 248
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/jez.1402480110

✦ Synopsis

Female rainbow trout were rendered either hypothyroid by ipodate injection or hyperthyroid by immersion in a 3,5,3'-triiodo-L-thyronine (T,) solution or by feeding T3-supplemented pellets, and ovarian function was evaluated from the gonadosomatic index (gonad weight . l o 2 * body weight-' = GSI), plasma 17P-estradiol (E,) level, or the ability in vitro of ovarian pieces to release E2 in the presence of salmon gonadotropin (sGtH). Hypothyroidism for 7 or 22 days depressed GSI or in vitro ovarian E2 release. Modest hyperthyroidism for 7 or 22 days, which raised plasma T3 from 1.6-3.3 ngiml (controls) to 4.1-7.7 ngiml, significantly increased GSI and in vitro ovarian E2 release. However, at higher TB levels (21-33 ng/ml) there was no increase in GSI and either no increase or a significant decrease in ovarian Ez release. None of these treatments altered the plasma E, levels although T3 treatment significantly enhanced the effect of injected sGtH in elevating El level. It is concluded that T, at physiologic levels enhances ovarian growth and GtH stimulation of E, production, but when plasma T, levels exceed those required to saturate putative