The influence of paraquat on the in vivo incorporation of lecithin precursors in lung tissue and ‘alveolar’ lecithin

Abstract

Rats were injected with paraquat (1,1′-dimethyl-4,4′-bipyridyliumdichloride, 35 mg/kg) and killed 14 or 48 h later. Twelve hours prior to sacrifice labelled choline or palmitic acid was injected. Immediately after sacrifice alveolar lavage was performed in situ and the lungs were removed and homogenized. Lipid extracts from lavage fluid and lung homogenates were prepared and their lecithin content analysed by thin layer chromatography. Lecithin was quantitated by phosphorous determination, the incorporation rate of the lecithin precursors in ‘alveolar’ and lung tissue lecithin was measured by liquid scintillation, and the fatty acid composition of lecithin was determined by gas liquid chromatography. In comparison with controls, the content of lecithin was reduced in lavage fluid from paraquat-injected rats. These animals also had reduced incorporation of choline in alveolar lecithin. The rate of incorporation of palmitic acid was the same in experimental animals and controls, so was the incorporation of choline in lung tissue lecithin. The findings suggest that paraquat interferes with the synthesis of alveolar lecithin by the phosphocholine transferase pathway, but not with the formation of lung tissue lecithin.

Key Words:

• choline
• experimental respiratory distress
• lecithin
• lung lipid metabolism
• palmitic acid
• pulmonary surfactant