Effects of calcium on a parathyroid hormone-sensitive adenylate cyclase inhibitor |
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Authors: | Tai C Chen Michael Rosenblatt Jules B Puschett |
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Institution: | 1. Renal-Electrolyte Section, Department of Medicine, University and Veterans Administration Hospitals, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205 USA;2. the Endocrine Unit, Massachusetts General Hospital, Boston, Massachusetts 02114 USA;3. Harvard Medical School, Boston, Massachusetts 02114 USA |
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Abstract: | Inhibition of parathyroid hormone (PTH)-sensitive adenylate cyclase by {Nle-8, Nle-18, Tyr-34} bPTH-(3–34) amide was studied in thyroparathyroid-ectomized dogs. The inhibitory effect was shown to be markedly enhanced by the addition of calcium ions into the assay system. At 0.1 mM Ca2+, complete inhibition by the antagonist was obtained. Chelation of exogenous Ca2+ by EGTA eliminated the Ca2+-induced inhibition. Both the basal and hormone-stimulated activities were decreased in the presence of 0.1 mM Ca2+, whereas the addition of EGTA increased both activities. Our results suggest that Ca2+ modulates canine renal PTH-sensitive adenylate cyclase and its inhibition by substituted bPTH-(3–34). |
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Keywords: | PTH parathyroid hormone bPTH bovine parathyroid hormone EGTA ethylene glycol bis (β-aminoethyl ether) N N N′ N′ tetraacetic acid EDTA ethylenediaminetetraacetic acid Nle norleucine |
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