Calcitonin and calcium ionophores: cyclic AMP responses in cells of a human lymphoid line.

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Abstract
Receptors for calcitonin, as assayed by the specific binding of 125I-labeled salmon calcitonin and stimulation of cyclic[c]AMP formation, were found in 8866 cells derived from a human lymphoid line. The affinity of calcitonin from different species and of various analogs of human calcitonin for the binding sites and their ability to stimulate cAMP formation were closely related to their hypocalcemic activity and presumably reflected biological properties of the hormones. Besides calcitonin, prostaglandin E1 and .beta.-adrenergic catecholamines stimulated cAMP formation in these cells. The Ca ionophores, A23187 [2-[(3.beta.,9.alpha.,11.beta.-trimethyl)-8-(2-pyrrolecarboxymethyl)-1,7-dioxaspiro[6.6]undecyl-2.beta.-methyl]-5-methylaminobenzoxazole-4-carboxylic acid] and Br-X-537A [bromo-lasalocid] did not influence the specific binding of 125I-labeled salmon calcitonin. A23187, however, suppressed basal and calcitonin-stimulated formation of cAMP in the presence of at least 0.6 mM Ca in the incubation medium. Br-X-537A did not require extracellular Ca to suppress basal and calcitonin-stimulated formation of cAMP, so the release of Ca from internal stores may regulate adenylyate cyclase activity in 8866 cells.