Dynamics of uptake and channeling of arachidonic acid in hamster alveolar macrophages and the effect of bleomycin on arachidonyl distribution

Abstract

The uptake and distribution of [ 14C]-arachidonic acid (AA) by primary culture hamster alveolar macrophages (AM) were examined. The macrophages were incubated for 2 to 18 hrs in RPMI-1640 medium containing 0.1% BSA and [ 14C]-AA. The uptake of [ 14C]-AA by AM was rapid with 71% and 83% of exogenous [ 14C]-AA taken up after 2 and 4 hrs of incubation, respectively. Initially, the uptaken [ 14C]-AA was equally distributed between phospholipids (PL) and neutral lipids (NL). However, by 8 hrs, 86% and 14% of [ 14C]-AA was found in PL and NL, respectively. This distribution pattern remained constant through 18 hrs. Within the PL pool, most of the [ 14C]-AA was initially incorporated into phosphatidylcholine (PC). However, with time, as the percent of [ 14C]-AA incorporated in PC declined, the percent incorporated in phosphatidylethanolamine increased. The incorporation of [ 14C]-AA into sphingomyelin, phosphatidylinositol, and phosphatidylserine remained constant with time. Within the NL, most of the [ 14C]-AA was initially found incorporated into triacylglycerols (TG). After 4 hrs, the percent of [ 14C]-AA found in TG decreased markedly, while the percent found in cholesterol esters markedly increased. Incubation of AM prelabeled with [ 14C]-AA with bleomycin at 0.5, 5, 50 and 500 μM for 2 and 8 hrs failed to have any effect on the distribution of [ 14C]-AA in PL and NL pools.