chlortetracycline and obelin

The aim of this paper is critically to evaluate the existing evidence for the role of intracellular Ca2+ in polymorphonuclear leucocyte (PMN) activation and in particular in oxygen radical production. Indirect experiments are based on the manipulation of extracellular Ca2+, measurement of 45Ca fluxes, employing pharmacological agents such as Ca2+-ionophores and intracellular Ca2+ antagonists and monitoring chlortetracycline fluorescence. Experiments of this type do not provide the necessary definitive evidence that an increase in intracellular Ca2+ is the trigger for PMN activation. Recent direct measurements of intracellular free Ca2+ using the Ca2+-activated photoprotein, obelin, and the Ca2+-sensitive fluorescent indicator, quin 2, have provided evidence for the existence of two distinct mechanisms of activation, one triggered by a rise in intracellular Ca2+ and the other independent of a rise in intracellular Ca2+. The source of the Ca2+ for the former mechanism is mainly extracellular but can also come from an intracellular Ca2+ store.

Topics: Aminoquinolines; Animals; Calcium; Calcium Channel Blockers; Calcium Radioisotopes; Chlortetracycline; Fluorescent Dyes; Free Radicals; Histocytochemistry; Humans; Ionophores; Luminescent Proteins; Neutrophils; Oxygen; Subcellular Fractions