Pulmonary vascular pressure profile in 2-3-week-old, 5-6-week-old and adult ferrets

We have previously reported age-related differences in the pattern of vascular pressure drop in rabbit lungs (Raj et al., Pediatric Res. 20:1107-1111, 1986). The purpose of this study was to investigate if there were similar age related differences in the ferret lung. To determine the profile of vascular pressures and the longitudinal distribution of vascular resistance in arteries, microvessels and veins, we isolated and blood perfused lungs of 20 ferrets (8 adults greater than 6 months of age; six 5-6-week-old and six 2-3-week-old). All lungs were perfused under similar experimental conditions with blood flow adjusted to keep pulmonary artery pressure constant at approximately 20 cmH2O, when left atrial pressure was 8 cmH2O. Lungs were inflated to 6 cmH2O airway pressure with a gas mixture so that blood Po2 was greater than 100 Torr. Microvascular pressure measurements were obtained in each lung in subpleural 20-50 microns diameter arterioles and 20-50 microns diameter venules using the micropipette servonull method. Blood flow achieved in all three groups of lungs was similar. We found that in adult ferret lungs, 40% of total vascular resistance was in arteries, 40% in microvessels and 20% in veins. In 2-3-week-old and 5-6-week-old ferret lungs, the fractional distribution of resistance in arteries, microvessels and veins was similar to that in adult ferret lungs. We conclude that, unlike in the rabbit, the pulmonary vascular pressure profile does not change with age in the ferret.