Effect of dietary (n-3) and (n-6) fatty acids on in vivo pulmonary bacterial clearance by neonatal rabbits.

Intrapulmonary bacterial clearance, lung inflammatory cell recruitment and macrophage superoxide generating capacity were studied in newborn rabbits nursed by their mother and given a supplement of either high [5 g/(kg.d)] or low [0.22 g/(kg.d)] doses of fish oil, safflower oil or saline for 7 d after birth. The high dose fish and safflower oil regimens diminished lung clearance of inspired Staphylococcus aureus by approximately 50% compared with the saline controls, but they did not alter lung neutrophil recruitment or alveolar macrophage bacterial phagocytosis. Only high dose fish oil decreased macrophage superoxide anion generation (by 30%). With high dose fish or safflower oil supplementation, the fatty acid content of lung parenchyma, bronchoalveolar lavage effluent and alveolar macrophages increased significantly. Low dose supplementation did not have this effect. We conclude that pharmacologic dietary (n-6) and (n-3) fatty acid supplementation impairs the ability of the neonatal rabbit lung to kill intrapulmonary S. aureus. It has been proposed that human infant formula be supplemented with fatty acids either to alleviate dietary deficiencies or to treat pulmonary inflammatory disorders. Based on our findings, the effects of such supplementation should be monitored relative to the possible heightened risk of bacterial infection.