Lipid synthesis by perfused lung

An isolated lung ventilated with pulses of negative pressure and perfused through the pulmonary vasculature was utilized for the study of 3-sn-phosphatidylcholine synthesis. The perfusion fluid consisted of a Krebs-Ringer phosphate buffer with 6% bovine serum albumin, pH 7.4, and the appropriate substrate. The simultaneous incorporation of (1-14C) palmitate and (2-3H) glycerol and the simultaneous incorporation of (CH3-14C) choline and (CH3-3H) methionine were examined. From these experiments it is concluded: 1) lung tissue incorporates (2-3H) glycerol into 3-sn-phosphatidylcholine to a greater extent than any other lipid examined; 2) both choline and methionine contribute to the synthesis of 3-sn-phosphatidylcholine, and 50-70% of the label in its nitrogen base is derived from choline and 30-50% from methionine; and 3) a high PO2 appears to reduce the synthesis of 3-sn-phosphatidylcholine.