Age-dependent change in arachidonic acid metabolic capacity in rat alveolar macrophages

Arachidonic acid (AA) metabolism was assessed in cultured alveolar macrophages (AM) obtained from newborn (10 days old) and adult (2 months and 4 months old) rats. The AMs were stimulated with the calcium ionophore, A23187 (10 microM). The released radiolabelled AA metabolites were measured by thin layer chromatography. The results showed that among different aged rats, the synthesis of 5-lipoxygenase (5-LO) metabolites, LTB4, LTC4, LTD4 and 5-HETE were increased with age inspite of similar levels of [14C]AA release. In response to A23187, 5-LO metabolic capacity of 2 and 4 months old adult rat AMs were increased 21-fold and 34-fold, respectively, compared with 10 days old rat AMs. As the metabolic capacity increased, the release of prostaglandins and thromboxane B2 tended to decrease markedly. Newborn rats (10 days old) AM, at the initial developmental stage, did not produce a noticeable amount of 5-LO metabolites which, conceivably, contribute to high susceptibility of neonatal lung to infection.