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.

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.