title: Parathyroid hormone receptors in circulating human mononuclear leukocytes.
abstract: In this article we demonstrate receptors for parathyroid hormone in circulating mononuclear leukocytes using the radioiodinated analogue (8,18 norleucine, 34 tyrosine) bPTH 1-34 (bovine parathyroid hormone 1-34). Specific binding, which is reversible and saturable, equilibrates within 5 min at 0-4 degrees C with a calculated KD of 8.9 X 10(-11) M. This binding has a pH maximum of 7.0, is magnesium-dependent, and is inversely related to medium calcium concentration. Such binding is completely inhibited by simultaneous addition of 4 ng/ml of bovine parathyroid hormone 1-34, 5 ng/ml of bovine parathyroid hormone 1-84, or 5 ng/ml (8,18 norleucine, 34 Tyr) of 3-34 bPTH, but is unaffected by a biologically inactive parathyroid hormone fragment or other unrelated peptide hormones. Cyclic AMP accumulation increases 3-fold after 5 min exposure of mononuclear leukocytes to bPTH 1-34 in concentrations as low as 1 X 10(-9) M. Lymphocytes appear to be the circulating cells which interact with PTH as indicated by the observations that: 1) lymphocyte-enriched preparations bind three times as much radioligand/cell as do mixed mononuclear leukocytes, 2) monocytes, platelets, granulocytes, and erythrocytes do not bind PTH, and 3) monocytes, but not lymphocytes, degrade the hormone.
mesh_terms: D002469:Cell Separation; D006801:Humans; D007700:Kinetics; D009000:Monocytes / Q000166:cytology / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000302:isolation & purification / Q000378:metabolism*; D018016:Receptors, Parathyroid Hormone
chemical_list: D010281:Parathyroid Hormone; D010446:Peptide Fragments; D011956:Receptors, Cell Surface; D018016:Receptors, Parathyroid Hormone; C032505:parathyroid hormone (1-34)amide, 8,18-Nle-34-Tyr-, bovine