Research Publications: UM-SG-RS-2003-15

Title:

Gonadal regulation of gonadotropin subunit expression and pituitary Lh protein content in female hybrid striped bass.

Year:

2003

Authors:

Klenke, U; Zohar, Y

DOI:

10.1023/B:FISH.0000030465.56876.97

Abstract:

To assess the response of the GtH system to the removal of gonadal feedback, effects of bilateral gonadectomy and 17beta-estradiol (E-2) replacement on gonadotropin (GtH) subunit expression, as well as LH protein levels, were monitored in the pituitary. Adult female hybrid striped bass undergoing mid-vitellogenesis were divided into one sham and two gonadectomized (gdx) groups. One gdx group received E-2 (2 mg kg^-1) via microspheric delivery systems, the other was given a vehicle injection. Groups were sampled on days 3 and 14 post-surgery (PS). Expression of all GtH subunits was significantly increased in the gdx group on both days compared to the shams, whereas E-2 replacement in gdx fish restored alpha and LHbeta mRNA levels to those of the sham fish and dramatically reduced FSHbeta mRNA levels. Gdx had no effect on the pituitary concentration of LH. E-2 replacement, however, reduced protein levels significantly on day 3, but not day 14. In conclusion, during mid-vitellogenesis expression of both GtHbeta subunits is negatively controlled by gonadal feedback, which is also evident by restoration of gdx subunit mRNA levels to those of the shams after E-2 replacement.

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