Alterations of Surfactant Pools in Fetal and Newborn Rat Lungs

Abstract

ABSTRACT. Preparation by the developing alveolar epithelium for the transition to air breathing and surfactant secretion at birth are critical components of neonatal survival. We combined morphometric analysis and biochemical assays of lung phospholipids to measure the amount and redistribution of lung surfactant during the perinatal period of rats. Within 10 min of the start of air breathing, there was a small increase in type I1 cell lamellar body content by morphometric and biochemical estimates. By 24 h, the whole lung and alveolar extracellular pool surfactant lipid had substantially increased. Subfractionation of the alveolar surfactant pool obtained at four times, from birth to 24 h of life, demonstrated a 20-fold increase in the ratio of phospholipid in a tubular myelin-rich fraction compared to a unilamellar vesicle-rich fraction. We conclude that packaging of surfactant may be very active immediately postbirth. Our results also indicate a major shift in the physical forms of extracellular surfactant during the first hours of air breathing. (Pediatr Res 21: 5-9, 1987) Abbreviations quantifying changes in the intracellular and extracellular pools of surfactant-associated phospholipid in the late fetal and newborn period, using morphometric and biochemical assays. METHODS Animals.Timed pregnant (previously virgin) Sprague-Dawley females (Zivic-Miller, Allison Park, PA) were received 5 to 7 days prior to parturition. During their late stages of pregnancy, they were allowed food and water ad libitum and were kept in 12-h light-dark cycles. The onset of labor was defined as behavior including nest building and agitation along with vaginal bleeding. Birth began shortly after nesting was complete and was allowed to progress uninterrupted until three to six fetuses were delivered. The air-breathing newborns were kept with the unanesthetized mother. The mothers were then anesthetized with 30-50 mg/kg pentobarbital intraperitoneally; the remaining fetuses were delivered individually through a hysterotomy. These fetuses (birth group) were more lethargic, but made limb motions. They were still connected to the placenta and made no respiratory efforts. The mothers continued spontaneous breathing during the entire procedure. DSPC, disaturated phosphatidylcholineNo more than 10 min passed before the newborns (+lo min PL, phospholipid group) were also anesthetized with intraperitoneal pentobarbital, LDH, lactate dehydrogenase the thoracic contents were rapidly removed and lung wet weight was obtained. Two or three unlavaged lungs were pooled for the LB DSPC' lamellar body disaturated phosphatidylcholine ~h o s~h o l i p i d determinations in all fetal animals. Pooled s a m~l e s -A -from these animals were regarded as a single determination. Since the +10 min group were expected to have developed in the lower poles of the uterus, we obtained lungs from fetuses in Immediately after birth, the newborn must transition to air the two lowest and the two highest uterine positions of four breathing and the effects this has on...

Surfactant Content and Type II Cell Development in Fetal Guinea Pig Lungs during Prenatal Starvation

“…volumes and their fractions of respiratory parenchyma were not 3) derives from the relatively small Percentage (10-2 1 %) of total significantly different between control and starved fetuses at d lung DPC that can actually be isolated from purified LB fractions 65 (Table 2). Ultrastructural analyses of type I1 cells indicated of the same lungs (21)(22)(23). The large m~o u n t of non-LB lung no significant interlobar differences for any animal, and data DPC is distributed elsewhere in type 11 cells (including endowere then pooled by animal for intergroup comparisons.…”

Changes in Alveolar Surface Area, Surfactant Protein A, and Saturated Phosphatidylcholine with Postnatal Rat Lung Growth

“…In the rat, there are increases in alveolar surfactant not associated with a loss of lamellar bodies from type I1 cells that imply complex relationships between intracellular and extracellular pools (12,28,29). Stevens et al (30) demonstrated that, at birth, secretion and surfactant phospholipid reuptake occurred simultaneously, with the net effect being a large increase in the alveolar pool on the first day of life.…”

Surfactant Treatment Effects on Lung Structure and Type II Cells of Preterm Ventilated Lambs

“…There also was no effect of surfactant treatment in that experiment. In term rats, Spain et al [27] reported that alveolar pools increased remarkably after birth, although biochemical or morphometric estimates of lamellar body pool size did not change. Similar morphometric analyses have been published by Faridy et al [28,29].…”