INFLUENCE OF OVARIECTOMY AND PHOTOSTIMULATION ON LEUTEINIZING HORMONEIN THE DOMESTIC TURKEY - EVIDENCE FOR DIFFERENTIAL REGULATION OF GENE-EXPRESSION AND HORMONE-SECRETION
Ml. Petrowski et al., INFLUENCE OF OVARIECTOMY AND PHOTOSTIMULATION ON LEUTEINIZING HORMONEIN THE DOMESTIC TURKEY - EVIDENCE FOR DIFFERENTIAL REGULATION OF GENE-EXPRESSION AND HORMONE-SECRETION, Biology of reproduction, 49(2), 1993, pp. 295-299
We have investigated the effects of ovariectomy (OVX) and photostimula
tion (PS) on anterior pituitary LHbeta mRNA abundance and circulating
levels of LH in the domestic turkey. The birds were divided into the f
ollowing four treatment groups: non-PS SHAM, PS SHAM, non-PS OVX, and
PS OVX. Photostimulation was initiated 7 days after OVX. Anterior pitu
itaries and blood samples were collected on Days 0, 1, 3, 7, 14, and 2
6 after PS. The experiment was terminated when the PS SHAM birds were
laying eggs regularly. Photostimulation of intact birds induced an inc
rease in both LHbeta mRNA levels (Days 3, 14, and 26 of PS) and serum
LH (Days 14 and 26 of PS; p < 0.05), while OVX of non-PS birds signifi
cantly elevated LH on Days 7, 10, 21, and 33 and LHbeta mRNA levels on
Days 7, 8, 10, 14, and 33 post-OVX. Circulating LH titers in the PS O
VX birds were well above the levels in the non-PS OVX group (p < 0.005
); however, LHbeta mRNA abundance was not significantly greater (p > 0
.05). Our results indicate that OVX and PS appear to be additive in st
imulating LH secretion but do not have this effect on LHbeta mRNA leve
ls. We have hypothesized that gonadectomy induces near-maximal accumul
ation of LHbeta mRNA and that therefore the subsequent stimulus of a l
ong photoperiod has no additional effect. We suggest that increases in
serum LH levels, beyond those of the OVX bird, may be controlled post
-transcriptionally.