Comparison of the effects of ATP, Mg2+, and MgATP on the release of luteinizing hormone-releasing hormone from isolated hypothalamic granules.
The effect of ATP, Mg2+, or MgATP on the release of luteinizing hormone-releasing hormone (LH-RH) from hypothalamic granules was examined under in vitro conditions. Granules, isolated from adult make hypothalami, were incubated at 37 degrees C in a buffered (pH 7.8) medium containing 0.15 M-KCl. The addition of ATP to the incubation mixture did not stimulate the release of LH-RH. In contrast, the addition of MgATP stimulated the release of LH-RH, the release being 62% greater than control. The addition of Mg2+ to the incubated granules also stimulated the release of LH-RH. However, the magnitude of this Mg2+-stimulated release of LH-RH was significantly (P less than 0.01) lower than that of the MgATP-stimulated release, indicating that ATP stimulates LH-RH release in a Mg2+-dependent manner. As both MgATP and Mg2+ alone stimulated LH-RH release, we characterized further these two release processes by incubating the granules under one of the following conditions: incubation at 4 degrees C in a buffered medium containing 0.15 M-KCl or incubation at 37 degrees C in a medium that does not contain KCl. Under these two incubation conditions, the MgATP-stimulated release of LH-RH was not manifested, whereas the Mg2+-stimulated release of LH-RH was manifested. On the basis of these differences, we propose that two different processes can lead to the release of LH-RH from isolated hypothalamic granules: one process involves ATP and Mg2+ (MgATP) and another process involves Mg2+ alone.
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology*; D008297:Male; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D013696:Temperature
D007987:Gonadotropin-Releasing Hormone; D011189:Potassium Chloride; D000255:Adenosine Triphosphate; D008274:Magnesium