title: Refractoriness of the pituitary gland after continuous exposure to luteinizing hormone releasing hormone.
abstract: The refractoriness of LH release by pituitary glands from intact female rats was studied during stimulation by luteinizing hormone releasing hormone (LH-RH), monobutyryl cyclic AMP+theophylline or potassium in vitro. Various concentrations of LH-RH (0.1, 0.3 and 10 ng/ml) all caused refractoriness within 24 h. Subsequent exposure to a supramaximally active concentration of LH-RH for 6 h also resulted in a depressed response; the degree of inhibition depended on the concentration of LH-RH to which the glands had been exposed previously. Glands made refractory to LH-RH also showed a depressed response to monobutyryl cyclic AMP+theophylline, although these agents by themselves were unable to induce refractoriness. Incubation in medium containing a high concentration of potassium also resulted in the release of LH, which in all respects was similar to that caused by LH-RH. Glands made refractory to LH-RH showed a decreased response to potassium and, conversely, the release of LH in response to LH-RH was reduced after exposure of glands to potassium. It is concluded that the LH releasing activity of LH-RH, which is mimicked by potassium, deteriorates during continuous exposure to the secretagogue.
mesh_terms: D000818:Animals; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D003864:Depression, Chemical; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D066298:In Vitro Techniques; D007986:Luteinizing Hormone / Q000378:metabolism*; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D013806:Theophylline / Q000494:pharmacology; D013997:Time Factors
chemical_list: D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D013806:Theophylline; D000242:Cyclic AMP; D011188:Potassium