Inhibition of polymorphonuclear leukocyte functions by chlortetracycline

Chortetracycline (CTC) inhibits chemotaxis, exocytosis and metabolic burst in rabbit polymorphonuclear leukocytes (PMNs), when these cells are activated in the absence of extracellular Ca2+. In the presence of extracellular Ca2+ CTC has little or no inhibiting effect on these functions. The inhibiting effect of CTC in the absence of Ca2+ occurs at concentrations which are not cytolytic. The inhibiting effect of CTC can be reversed by washing the cells or by addition of Ca2+ or Mg2+ to CTC-pretreated cells. Inhibition of the metabolic burst by CTC depends on the activator used. When phorbolmyristate acetate is used to activate the cells, the metabolic burst is inhibited at lower CTC concentrations than with chemotactic peptide as an activator. With due observance of the chemical properties of CTC and literature data about the requirement of intracellular Ca2+ for neutrophil functions, the results obtained are consistent with the view that CTC interferes with neutrophil functions, by complexing intracellular Ca2+, and that this inhibition is reversed when sufficient extracellular Ca2+ moves into the cell.