Zymosan, which is composed primarily of α-mannan and β-glucan polymers, is a well recognized activator of macrophages. The type receptor by which unopsonized zymosan induces arachidonic acid release was investigated. It was found that particulate β-glucan and zymosan stimulated an identical dose-dependent release of arachidonic acid. This release of arachidonic acid by zymosan was blocked by soluble β-glucans whereas soluble mannan had no effect. This inhibition was not due to a general toxic effect of the soluble β-glucans as they had no effect on calcium ionophore-induced release of arachidonic acid. β-glucan-induced fatty acid release from these cells was shown to be fairly specific for arachidonic acid. These data reveal that zymosan stimulates the specific release of arachidonic acid from rabbit alveolar macrophages, at least in part, via a β-glucan receptor.
