The effect of gonadotropin-releasing hormone (GnRH) and/or estradiol (E2) on pituitary messenger ribonucleic acid (mRNA) levels of luteinizing hormone β (LHP), follicle-stimulating hormone β (FSHP) and the common α-subunit were determined in anterior pituitary glands from ovariectomized (OVX) ewes. Hypothalamo-pituitary disconnected (HPD) ewes receiving appropriate hormonal treatment were used to assess the relative roles of GnRH and E2 in directly regulating FSHβ and α-subunit mRNA levels. Levels of LHβ mRNA were increased in OVX animals compared with intact controls, and E2 treatment of OVX animals significantly reduced mRNA levels of LHβ and FSHβ. HPD substantially reduced FSHβ and α-subunit mRNA levels. Treatment of OVX/HPD animals with pulses of GnRH (250 ng/2 h) for I week restored FSHβ and α-subunit mRNA to OVX levels. Combined GnRH and E2 treatment significantly lowered FSHp mRNA levels, but resulted in a rise in a-subunit mRNA levels. Treatment of OVX/HPD ewes with E2 alone had no effect on FSHβ and α-subunit mRNA levels. These findings indicate that E2 acts directly on the pituitary to negatively regulate FSHβ mRNA levels, and to positively regulate α-subunit mRNA levels in the presence of GnRH.
- Follicle-stimulating hormone
- Gonadotropin-releasing hormone
- Luteinizing hormone
- Messenger ribonucleic acid