1,10-Phenanthroline blocks LPS- and TNF-–stimulated release of CXCR1 cleavage products. Purified peripheral blood PMNs were preincubated with 1,10-phenanthroline (0.5 mmol/L) for 30 minutes in media (RPMI/10% fetal calf serum) followed by the addition of LPS (100 ng/mL) or TNF- (50 ng/mL) for 1 hour at 37°C. Cell supernatants were isolated, and the proteins were assayed on a 10% SDS-polyacryamide gel and electrophoretically transferred to PVDF membranes. The PVDF membrane shown was immunoblotted with polyclonal Ab recognizing the carboxy-terminal amino acids 341-359 of the CXCR1 molecule.