The membranous structures of the pulmonary extracellular lining were removed from the lungs of rabbits by pulmonary lavage and isolated by differential centrifugation. This membranous fraction contained 93% of the total extracellular phospholipids present in lavage effluents and consisted of membranous vesicles, membrane fragments, tubular myelin and secreted lamellar bodies. The fraction was rich in phosphatidylcholine (79.4%) containing 85.2% palmitic acid in the 1-position and 57.4% palmitic acid in the 2-position. Phosphatidylglycerol was the next most abundant phospholipid, accounting for 9.4% of the total. E.p.r. spectra, obtained by using 5-doxylmethylstearate as a probe, showed that the extracellular phospholipids of the pulmonary lining were organized into structures which were much more fluid than erythrocyte-ghost membranes. The fluidity of phosphatidylcholine isolated from the membranous fraction was similar to that of the fraction itself, indicating that the minor phospholipids had very little influence on the fluidity of the major phospholipid. At physiological temperature, the fluidity of dipalmitoyl phosphatidylcholine was relatively low, but could be markedly increased by the presence of 1-palmitoyl-2-oleoyl phosphatidylcholine or phosphatidylglycerol (10%). Protein present in the extracellular phospholipid fraction did not affect the fluidity of the fraction. These studies indicate that the unsaturated phosphatidylcholines could play a major role in determining the fluidity of the important surface-tension-lowering phospholipids such as dipalmitoyl phosphatidylcholine.

The mitochondria-rich fraction of the lung tissue is the most active subcellular fraction for the synthesis of long-chain fatty acids. This observation is contrary to what has been reported for the subcellular fractions of the liver. The high rate of fatty acid synthesis observed with the mitochondria-rich fraction of the lung may be related to the morphological transformation of mitochondria.

Chelating agents, when applicable, are the most effective means of removing radioactive particles from the lungs. The chemical form of the inhaled particles and their history before inhalation can alter the rate of clearance by these agents. Drugs which decrease mucus secretion or increase phagocytosis also merit further testing. Experiments with lraCela4Pr, 239Pu, and U supporting these conclusions will be presented and discussed.

No abstract

The size, turnover time and transfer rate of the glucose pool were estimated with glucose–C14 in normal and ketotic cows. The size and turnover time of the pool were both about 1/5 greater in the ketotic than in the normal cows, so that the transfer rate remained similar, being about 1 gm/min. The hypoglycemia which is characteristic of the disease appeared to be associated with an expansion of the glucose space, which in the normal cows approximated the extracellular volume, into the intracellular compartment of the ketotic cows. These results do not favor theories of bovine ketosis which presume a shortage of body glucose. Submitted on June 25, 1959