Effects of FMLP and LPS on [Ca2+]i of peritoneal exudate polymorphonuclear leukocytes following onset of inflammation

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Abstract
Because a general study of activated neutrophils may have relevance to periodontal diseases and accompanying inflammation, we studied a function of mouse polymorphonuclear leukocytes (PMNs) that exude into the peritoneal cavity in response to inflammation caused by i.p. injection of 2% casein. The effects of E. coli‐lipopolysaccharide (E‐LPS) and a chemotactic factor, N‐for‐myl‐N‐methionyl‐N‐leucyl‐L‐phenylalanine (FMLP), on the level of intracellular calcium ([Ca2+]i) in these PMNs were examined. From analysis made with a laser cytometer (ACAS 570), the PMNs in exudates harvested 3–9 h after the onset of inflammation were shown to undergo [Ca2+]i elevation in response to 10–6 M FMLP. The peak concentration of [Ca2+]i elicited by FMLP was highest in exudate cells 6 h after casein injection. In addition, about 65% of the PMNs in the 3‐h exudate were FMLP sensitive displaying an elevated [Ca2+]i, whereas more than 85% of them in 6‐ and 9‐h exudates became FMLP sensitive. Also, the maximum level of [Ca2+]i after FMLP stimulation was potentiated by pretreatment of the cells with E‐LPS (0.2 μg/ml). The present study suggests that PMNs induced by casein injection and appearing in mouse peritoneal exudate at different times possess significantly different ability to undergo [Ca2+]i elevation, and different susceptibility toward a chemotactic factor, FMLP.