Diacylglycerol kinase (DGK) catalyzes phosphorylation of diacylglycerol to generate phosphatidic acid, and both molecules are known to serve as second messengers as well as important intermediates for the synthesis of various lipids. In this study we investigated the spatiotemporal expression patterns of DGK isozymes together with the developmental changes of the mRNA expression and enzymatic property in rat lung. Northern blot analysis showed that mRNA for DGK, -, and - was expressed in the lung. By immunohistochemical examination, DGK and - were shown to be co-expressed in alveolar type II cells and macrophages. Interestingly, these isozymes were localized at distinct subcellular locations, i.e., DGK in the cytoplasm and DGK in the nucleus, suggesting different roles for these isozymes. In the developing lung, the expression for DGK and - was transiently elevated on embryonic day 21 (E21) to levels about 2~3-fold higher than on postnatal day (P0). On the other hand, the expression for DGK was inversely elevated about 2-fold on P0 compared with that on E21. These unique changes in the expression pattern during the perinatal period suggest that each isozyme may play a distinct role in the adaptation of the lung to air or oxygen breathing at birth.