The role of calcium in the initiation of superoxide release from alveolar macrophages

Andrij Holian, Ronald P. Daniele

Research output: Contribution to journalArticlepeer-review

Abstract

The role of calcium in the release of superoxide anion (O 2−) was examined in alveolar macrophages after stimulation with the Soluble stimuli: concanavalin A (Con A), N‐formyl methionyl phenylalanine (FMP), and the calcium ionophore, A23187. The release of O 2− by Con A was unaffected over a wide range of extracellular calcium concentrations (20 μM to 3 mM), whereas increasing the extracellular calcium above 2 mM inhibited FMP‐stimulated O 2− release. In contrast, A23187 did not stimulate O 2− release in calcium‐free medium (≤ 30 μM). The addition of EGTA (50 μM) to calcium‐free medium had no effect on Con A stimulation of O 2− release or FMP‐stimulated O 2− release. These results suggest that, for the three soluble stimuli, there are different roles for Ca+2 in the activation and transmission of stimulatory signals across the cell membrane. Con A‐ or FMP‐stimulated calcium efflux from calcium‐loaded cells in either calcium‐free medium or 0.5 mM calcium‐containing medium. In calcium‐free medium, FMP transiently retarded 45Ca+2 uptake, while in 0.5 mM calcium‐containing medium, FMP transiently stimulated 45Ca+2 uptake. For either Con A or FMP, calcium efflux preceded O 2− release by 30–45 sec. Quinine, an agent that blocks membrane hyperpolarization in macrophages, completely blocked O 2− release by concanavalin A or FMP and inhibited 45Ca+2 efflux by 50% or more for both agents. These results support the hypothesis that redistribution of cellular Ca+2 is one of the initial steps leading to the release of O 2−.

Original languageEnglish
Pages (from-to)87-93
Number of pages7
JournalJournal of Cellular Physiology
Volume113
Issue number1
DOIs
StatePublished - Oct 1982

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