MUSCARINIC CHOLINERGIC RECEPTORS ON CULTURED THYROID-CELLS .2. CARBACHOL-INDUCED DESENSITIZATION

  • 1 January 1982
    • journal article
    • research article
    • Vol. 21  (1) , 73-77
Abstract
Muscarinic cholinergic receptors were previously characterized on cultured porcine thyroid cells. The receptor number was increased by chronic thyrotropin or prostaglandin E2 treatment. The long-term effect of carbachol was studied. After chronic treatment with carbachol, cells were completely desensitized to acute carbachol stimulation. This process was blocked by muscarinic antagonists. A complete desensitization was obtained after 6 h of treatment with 100 .mu.M agonist. Under these conditions the quinuclindinyl benzilate binding capacity of cell homogenates was reduced by 50%. Withdrawal of carbachol allowed the complete restoration of the sensitivity of cells within 6 h with only a partial recovery of the binding capacity (25%). The complete complement of receptors was obtained after 24 h of recovery. Desensitization and agonist-induced decrease in receptor number were not affected by cycloheximide, whereas the recovery of both effect and binding sites required active protein synthesis.