ANALYSIS OF LUNG SURFACTANT IN THE METAMORPHOSING BULLFROG (RANA-CATESBEIANA)

In bullfrog (Rana catesbeiana) tadpoles, the lung begins to function a t an advanced stage of metamorphosis. As a preliminary step for invest igation of the mechanisms involved in lung maturation, pulmonary surfa ctant was prepared from tadpoles at advanced stages of metamorphosis a nd its biochemical properties were analyzed. Surfactant phospholipid a nalysis revealed that the major constituent was phosphatidylcholine (P C), as examined in the animals at late climax (stage 24). Other detect able phospholipids were phosphatidylethanolamine, phosphatidylserine, sphingomyelin, and phosphatidylglycerol, a marker lipid in mammalian s urfactant. As in mammals, PC in the surfactant was rich in saturated f atty acids, about 50% of fatty acid moieties being palmitic acid. The content of surfactant PC in the lung increased moderately around mid-c limax and markedly at the end of climax. The effect of antiserum again st bullfrog prolactin (PRL) on the pulmonary surfactant was studied in climactic tadpoles. The content of surfactant PC in the lung of the a ntiserum-treated larvae was lower than that in the lung of the normal rabbit serum-injected larvae, whereas the content of PC in the whole l ung did not differ between the antiserum-treated and control groups. T he results suggest that synthesis of surfactant in the amphibian lung is enhanced as metamorphosis progresses and that PRL is involved in lu ng maturation. (C) 1994 Wiley-Liss, Inc.