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Prostaglandin synthesis and release by subpopulations of rat interstitial macrophages.

Recent data indicate that interstitial macrophages are not functionally homogeneous, but are heterogeneous with several subpopulations that differ both morphologically and functionally. Furthermore, interstitial macrophages are believed to be precursor to alveolar macrophages, which have recently been shown to be heterogeneous in their ability to synthesize and release prostaglandins. Considering the apparent importance of prostaglandin synthesis and release in inflammatory and immune responses, the current study was undertaken to determine if interstitial macrophage subpopulations differ in their ability to synthesize and release prostaglandin (PG) E, PGI2, and thromboxane (Tx) A2 after stimulation by calcium ionophore A23187, zymosan, or aggregated IgG. Interstitial macrophages were harvested and separated into 18 density-defined fractions. Density-defined interstitial macrophages (DD-IM) showed marked heterogeneity in prostaglandin synthesis and release. Maximal PGE synthesis and release was seen as a single broad peak after calcium ionophore A23187 and zymosan stimulation. In contrast, no peak in PGE synthesis was seen after aggregated IgG stimulation. PGI2 synthesis also was seen as a single broad peak generated by the lower density interstitial macrophage subpopulations after all stimuli. Similarly, TxA2 synthesis and release was maximal from a broad range of various DD-IM after calcium ionophore A23187, zymosan, and aggregated IgG stimulation. Furthermore, the synthesis and release of TxA2 correlated with the presence of zymosan and IgG receptors on DD-IM. The results demonstrate that DD-IM are heterogeneous in ability to synthesize and release prostaglandins, which are dependent on the stimuli.