Effects of age and breed on the phospholipid composition of canine surfactant.

To investigate possible age- and breed-related changes in the composition of canine pulmonary surfactant, we determined the phospholipid patterns of surfactants isolated by bronchoalveolar lavage of 3 age categories of beagles (3-7 months; 3-7 years; 12 years and older) and of 1 group of greyhounds (4-14 years). There was a significant (p = 0.01) increase in the proportion of phosphatidylcholine in surfactant with age, whereas the proportions of phosphatidylserine and sphingomyelin were significantly lower in old beagles compared to young dogs. Although the differences were generally rather small, they may nevertheless be of biological importance, as was indicated by comparing the minimal surface tensions of lavage fluids obtained from young and old beagles. It is attractive to speculate that the shift in surfactant lipid composition could be 1 of the mechanisms that permit efficient lung function in old dogs, despite changes in morphology and mechanics in the aging lung. The phospholipid composition of surfactant isolated from greyhounds differed significantly from that in beagles. The surfactant of greyhounds was enriched in phosphatidylglycerol compared to all age groups of beagles. The degree of saturation of surfactant phosphatidylcholine was also higher in greyhounds, although this differences was significant only when compared to young and middle-aged beagles.