No abstract

ABSTRACT. Most previous studies of the relationship between surfactant and growth have correlated surfactant pool size with lung weight or body weight. We asked how the quantities of the surfactant components surfactant protein A (SP-A) and saturated phosphatidylcholine (Sat PC) recovered by alveolar wash changed with age in relationship to morphologic measurements of alveolar surface area in rats. We also calculated SP-A and Sat PC in total lung per surface area. In groups of three to 14 rats studied on d 1,7,14,21,50, and 100 of age, the ratio of alveolar surface area to body weight was highest at d 14 and lowest at d 100. Alveolar and total lung SP-A and Sat PC were higher relative to body weight and surface area on d 1 than at all other ages. Alveolar and total lung SP-A peaked relative to surface area at d 21 and subsequently decreased significantly at d 100. The alveolar Sat PC to surface area ratio also was highest at d 21 and decreased significantly at d 50 and 100. The SP-A to Sat PC ratio in alveolar washes was not constant across this age range, being highest at d 21 and 50. These measurements demonstrate age-dependent changes in alveolar and total lung SP-A and Sat PC in the rat that continue beyond the newborn period. (Pediatr Res 35: 685-689,1994)

The effects of exogenous surfactant treatment combined with postnatal ventilation on surfactant protein (SP)-A, SP-B, and SP-C steady-state mRNA levels were evaluated in preterm sheep at 120, 132, and 139 days gestation. Three groups were studied at each gestation period: animals ventilated and treated with 100 mg/kg natural sheep surfactant, animals ventilated and not treated with surfactant, and a comparison group of lambs that were neither ventilated nor treated with surfactant. In unventilated lambs, SP-A and SP-C mRNA levels measured by densitometry from Northern blots increased between 120 and 132 days gestation (P < 0.05). At 120 days gestation, no differences in SP-A, SP-B, or SP-C mRNA levels were noted among the three groups. At 132 days gestation, SP-A mRNA levels increased in both ventilated groups (P < 0.01), but no additional surfactant effect on SP-A mRNA expression was detected. There were no changes in SP-B or SP-C mRNA levels among the groups at 132 days gestation. At 139 days gestation, mRNA levels for both SP-A and SP-B increased after ventilation, compared with the unventilated groups (P < 0.05). Furthermore, an additional effect of surfactant treatment to increase SP-A mRNA levels relative to animals undergoing ventilation alone was noted (P < 0.05). We conclude that postnatal changes in mRNA levels for the surfactant proteins are gestationally regulated and protein specific.