Effects of chicken (Gln8)- and mammalian (Arg8)-luteinizing hormone-releasing hormones on the release of gonadotrophins in vitro and in vivo from the adenohypophysis of Japanese quail
ABSTRACT Both chicken luteinizing hormone-releasing hormone (Gln8-LH-RH) and mammalian luteinizing hormone-releasing hormone (Arg8-LH-RH) increased the release of FSH and LH from adenohypophysial halves of adult male Japanese quail when the halves were incubated in a medium containing LH-RH. Elevation of the FSH release was less marked than that of the LH release irrespective of the LH-RH species. A pulse stimulation (10 min) of adenohypophysial halves with chicken as well as mammalian LH-RH in vitro resulted in a burst of both FSH and LH release. The increment of the FSH release was smaller than that of the LH release. A single intravenous injection of each LH-RH to adult male quail induced rapid increases of plasma FSH and LH levels within 5 min. The plasma levels of FSH and LH returned to their initial levels at varying times after the injection depending on the dose of LH-RH. Again, the increment of the FSH level was smaller than that of the LH level, showing a similar profile to the in vitro pulse stimulation experiment. No significant difference in ability to stimulate FSH and LH secretions from the quail adenohypophysis was detected between chicken and mammalian LH-RHs under either in vivo or in vitro conditions, whereas chicken LH-RH has been reported to be far less potent than mammalian LH-RH when tested on the rat adenohypophysis.
Article: Influence of ovariectomy and photostimulation on luteinizing hormone in the domestic turkey: evidence for differential regulation of gene expression and hormone secretion.[show abstract] [hide abstract]
ABSTRACT: We have investigated the effects of ovariectomy (OVX) and photostimulation (PS) on anterior pituitary LH beta mRNA abundance and circulating levels of LH in the domestic turkey. The birds were divided into the following four treatment groups: non-PS SHAM, PS SHAM, non-PS OVX, and PS OVX. Photostimulation was initiated 7 days after OVX. Anterior pituitaries and blood samples were collected on Days 0, 1, 3, 7, 14, and 26 after PS. The experiment was terminated when the PS SHAM birds were laying eggs regularly. Photostimulation of intact birds induced an increase in both LH beta 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 significantly elevated LH on Days 7, 10, 21, and 33 and LH beta mRNA levels on Days 7, 8, 10, 14, and 33 post-OVX. Circulating LH titers in the PS OVX birds were well above the levels in the non-PS OVX group (p < 0.005); however, LH beta mRNA abundance was not significantly greater (p > 0.05). Our results indicate that OVX and PS appear to be additive in stimulating LH secretion but do not have this effect on LH beta mRNA levels. We have hypothesized that gonadectomy induces near-maximal accumulation of LH beta mRNA and that therefore the subsequent stimulus of a long photoperiod has no additional effect. We suggest that increases in serum LH levels, beyond those of the OVX bird, may be controlled post-transcriptionally.Biology of Reproduction 09/1993; 49(2):295-9. · 4.01 Impact Factor