A New More Potent Analogue of LH-RH

[Des-Gly-NH₂¹⁰, Pro-ethylamide⁹]-LH-RH

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The effect of a new anaiogue [Des-Gly-NH₂¹⁰, pro-ethylamide⁹]-LH-RH (TAP-031) on the release of LH and FSH was compared with the effect of synthetic LH-RH by both the in vivo and in vitro assay method. The concentration of FSH and LH in serum and medium was determined by NIAMD-rat hormone radioimmunoassay kits. Single intravenous injections of 1, 10, 100 and 1, 000mμg of TAP-031 in ovariectomized-estrogenprogesterone blocked rats (O.E.P.), induced the increases of serum LH 5 to 60min after injection. In contrast, single injections of the same four doses of LH-RH in O.E.P. rats induced the increase of serum LH at 5 to 30min after injection. Intravenous single injections of 1 and 10mμg of TAP-031 and LH-RH induced no significant elevations of serum FSH in O.E.P. rats. However, injections of 100 and 1, 000mμg of TAP-031 and LH-RH induced significant elevations of serum FSH 1 to 2 hrs after injection of TAP-031, and 10 to 60min after the injection of LH-RH, respectively. The appearance of peak in serum LH and FSH was remarkably postponed in administration of over 100mμg of TAP-031. The increase in serum LH and FSH was larger in administration of TAP-031 than in administration of LH-RH.
In in vitro rat pituitary incubation experiments, LH and FSH releasing activities of TAP-031 were shown to be stronger than those of LH-RH.
These data offer the evidences demonstrating that TAP-031 has the stronger and more prolonged LH and FSH releasing activities both in vivo and in vitro than synthetic LH-RH.