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Effect of Vagal Denervation on Sleep States, Cardiorespiratory Responses and Surfactant System during Postnatal Period

Injection of interleukin-1α (IL- 1α) into the amniotic fluid accelerates the maturation of the surfactant system, improves the lung stability after premature birth, and upregulates the expression of surfactant protein A (SP-A) and SP-B. According to preliminary study, IL-1α increases SP-A mRNA in explants of the immature lung (Pediatr Res 37:61A, 1995). The aim of the present study was to investigate the mechanism of the IL-1 induced increase in SP-A mRNA.

At a gestational age of 27.9 days, pregnant rabbits were infused with enprofylline, a new xanthine with potent antiasthmatic effects. Following a priming dose of 5 mg/kg, 20 mg/kg were infused over a 2-h period. Controls received Ringer's solution. On completion of the infusion, the fetuses were delivered and the effect on their surfactant system was evaluated. Surface tension in airway fluid, measured with the pulsating bubble surfactometer, at minimal bubble size in the third cycle, was 21.8 +/- 2.2 (mean +/- SE) versus 28.7 +/- 1.7 mN m-1 (p less than 0.01). Pressure-volume loops of the lungs of the fetuses showed that at a deflation pressure 10 cm H2O the volume was 64 +/- 3 versus 49 +/- 3% (p less than 0.0005). The lung lavage fluid had a phospholipid phosphorus content of 41.9 +/- 3.8 versus 18.5 +/- 1.3 micrograms/g dry lung (p less than 0.0005). The values indicate that enprofylline caused a release of surfactant into the fetal airways.

Alveolarization in the rat occurs during the first 21 days and provides surface area proportional to oxygen needs. Lung size is known to increase in distance runners and persons living at altitude. Rat dams with 7–1 day old pups (HR), were placed 0.12 Ox in a recirculating chamber using Nx to reduce O2 and soda lime to absorb CO2. Control dams and comparable litters of pups (CR) were raised in 0.21 O2 under similar conditions. At 20–21 days HR and CR pups were weighed, injected with [14C] methylcholine, and the lungs removed, weighed, and homogenized. A lamellar body (LB) fraction was derived by sucrose density centrifugation and LB disaturated phosphatidylcholine (LBPC) was extracted, quantitated, and the specific activity determined. HR pups were hyperpneic and runted significantly as compared to CR (36.1g vs 51.4g, p