Abstract
The novel calcium ionophore chlortetracycline (CTC) induced histamine secretion (less than or equal to 90%) from isolated rat peritoneal mast cells in a pH and dose-dependent fashion. The process was dependent on exogenous calcium ions and was inhibited by extremes of temperature and metabolic blockers. The release was rapid, being essentially complete within 1 min, but the half-life of the process varied inversely with the concentration of the ionophore. In contrast to receptor-mediated ligands, but in keeping with other ionophores, the activated state induced by CTC did not decay with time. The secretion was effectively inhibited, according to the concentration of the ionophore, by disodium cromoglycate and other anti-allergic or cyclic AMP-active drugs. These results confirm our previous contention that these agents do not act on receptor-mediated calcium-channels. CTC induced a significant (less than or equal to 50%) release of histamine from enzymically dispersed rat mesenteric mast cells but was essentially inactive against isolated mast cells from the mesentery or lung of the guinea-pig. These results extend our former observations on the functional heterogeneity of mast cells and show that, in common with other secretagogues, ionophores may exhibit selectivity in their mode of action.
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