Tracheal fluid in fetal lambs: spontaneous decrease prior to birth

Kitterman, Joseph A.; Ballard, Pl; Clements, John A.; Mescher, E. Joseph; Tooley, William H.

doi:10.1152/jappl.1979.47.5.985

Cited by 126 publications

(35 citation statements)

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“…Despite the fact that physiologic intravascular expansion has not been shown to mediate a similar response, reports suggest that events before birth may be associated with net fluid shift into the intravascular space. Specifically, decreased lung fluid production has been documented in the lamb 2 d before delivery (18). In addition, increased intrauterine hydrostatic pressure associated with labor could expand the intravascular vol and increase ANF secretion as observed with water immersion therapy (19,20).…”

Section: Resultsmentioning

confidence: 99%

Atrial Natriuretic Factor During the Perinatal Period: Equal Depletion in Both Atria'

1989

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ABSTRACT. Data in the literature concerning atrial natriuretic factor (ANF) physiology in the fetus and newborn, although limited, suggest significant activity during the perinatal period. To characterize further ANF physiology during this time, we documented immunoreactive ANF (IR-ANF) concentrations in the right and left atria before and immediately after birth a s well as in the hearts of immature and adult rats. There was a significant decrease in the concentration of IR-ANF in both right and left atria on the In contrast to normal adult animals, factors mediating the observed change affect both atria equally during the perinatal period. The concentration of IR-ANF in the right and left atrium of the fetal, newborn, and immature animals was equal. These data document significant alterations in intraatrial IR-ANF concentrations in the perinatal period. The changes in tissue concentration reflect an alteration in the synthesis/release relationship that may be either a response to or evidence of involvement in the modulation of intravascular vol at the initiation of extrauterine life. (Pediatu Res 25339-341, 1989) Abbreviations ANF, atrial natriuretic factor IR-ANF, immnnoreactive atrial natriuretic factor ANF, a peptide synthesized and secreted by atrial myocytes, has potent natriuretic, diuretic, vasodilatory, and antimineralocorticoid properties (1 -7). These characteristics suggest that ANF may play a significant role in salt and water homeostasis and in blood pressure control (1,8).Data in the literature concerning ANF physiology in the fetus

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Section: Resultsmentioning

confidence: 99%

Atrial Natriuretic Factor During the Perinatal Period: Equal Depletion in Both Atria'

1989

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“…Fluid secretion into fetal lamb and guinea pig lungs decreases before birth (13,27,39,48) simultaneously with the appearance of endogenous catecholamines and stress hormones. ␤-Adrenoceptor agonist stimulation is thought to increase transepithelial Na ϩ transport by increasing ENaC activity at the apical side of alveolar epithelial type II cell (4) and by increasing the number and activity of the Na-KATPases in the basal membrane of the alveolar epithelial type II cell (42).…”

Section: Discussionmentioning

confidence: 99%

Oxytocin-induced labor augments IL-1β-stimulated lung fluid absorption in fetal guinea pig lungs

Nair¹,

Li²,

Bhattacharjee³

et al. 2005

American Journal of Physiology-Lung Cellular and Molecular Phys

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-We tested the hypothesis that oxytocin-induced labor augmented IL-1␤-induced/ -stimulated lung fluid absorption in preterm guinea pig fetuses. IL-1␤ was administered subcutaneously daily to timed-pregnant guinea pigs for 3 days with and without simultaneous cortisol synthesis inhibition by metyrapone. At day 3, oxytocin was administered, and fetuses were delivered by abdominal hysterotomy at 61 and by oxytocin-induced birth at 68 days gestation. Delivered fetuses were instilled with isosmolar 5% albumin into the lungs, and lung fluid movement was measured over 1 h by mass balance. Lung fluid absorption was induced in 61-day and stimulated in 68-day gestation lungs by IL-1␤. Labor induction by oxytocin augmented IL-1␤-induced/-stimulated lung fluid absorption. Metyrapone pretreatment did not affect oxytocin-induced/-stimulated lung fluid absorption, while completely blocking IL-1␤-induced/-stimulated fluid absorption. Fetal lung fluid absorption, when present, was always propranolol and amiloride sensitive, suggesting that ␤-adrenoceptor stimulation and amiloridesensitive sodium channels were critical for fluid absorption. Epithelial sodium channel and Na-K-ATPase subunit expressions were both increased by IL-1␤, but not further by oxytocin. Our results indicate that IL-1␤ release into the maternal blood circulation positively affects lung maturation due to the IL-1␤-induced release of cortisol and thus prepares the lungs for the epinephrine surge associated with labor.␤-adrenoceptors; cortisol; epinephrine; prenatal lung development; sodium transport CYTOKINES, SUCH AS INTERLEUKIN-1 (IL-1), can be important during pregnancy, because IL-1 has been detected in the placenta and amniotic fluid (12,44). In this regard, interleukins have been proposed as a signal for parturition onset, as cytokines can stimulate prostaglandin biosynthesis (41). During normal pregnancies, IL-1 is present in the amniotic fluid in low concentrations, but during preterm labor much higher amniotic fluid IL-1 concentrations are present (44). Intrauterine infection/inflammation may further elevate cytokine levels, the highest activity being attributable to IL-1␤ (44). Many prematurely born infants suffer from fetal infection and/or respiratory distress syndrome (RDS), both of which are important reasons for mortality of premature babies. Recent human data suggest that ion transport abnormalities across lung epithelial cells, i.e., an incomplete transition of lung fluid secretion to lung fluid absorption, can contribute to RDS development (1). Factors accelerating ion transport across alveolar cells may thus have benefits for the resolution of RDS. Recent experimental data have suggested that proinflammatory cytokines could also promote lung maturation (9,14,26,47). IL-1␣ increased mRNA surfactant protein expression and improved lung compliance in fetal rabbits (9). IL-1␣ also improved postnatal lung function with increased surfactant pool size without eliciting systemic inflammatory responses in lambs (14, 47). We recently reported that IL-...

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“…Lung fluid production slows in late gestation (2). At the time of birth, changes in airway ion transport facilitate the adaptation to postnatal life and air breathing (3).…”

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confidence: 99%

Airway Ion Transport on the First Postnatal Day in Infants Delivered Vaginally or by Elective Cesarean Section

et al. 2003

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To determine airway ion transport in term infants on the first day of postnatal life, and to test the hypothesis that infants born without labor have reduced sodium absorption, we measured nasal potential difference using a modified perfusion protocol suitable for newborn infants. We examined maximal stable baseline potential difference, the change after perfusion with 10 Ϫ4 M amiloride (⌬amil), and the change after perfusion with a zerochloride solution (⌬zero Cl Ϫ ) in infants born after elective cesarean section (n ϭ 21) or normal labor (n ϭ 20). Maximal stable baseline potential difference was not different in the two cohorts (Ϫ24.0 mV, range Ϫ9 to Ϫ64 mV versus Ϫ25.5 mV, range Ϫ6 to Ϫ44 mV). The majority of infants in both cohorts showed a substantial fall in potential difference after amiloride perfusion, and there was little capacity for chloride secretion. These results demonstrate a fluid absorptive pattern in the airways on the first postnatal day. In these well infants, the ion transport phenotype was not dependent on the presence or absence of labor. The fetal lung is filled with fluid, secreted by pulmonary epithelial cells through active Cl Ϫ transport into the bronchial lumen with water moving along the osmotic gradient (1). Lung fluid production slows in late gestation (2). At the time of birth, changes in airway ion transport facilitate the adaptation to postnatal life and air breathing (3). Chloride ion secretion slows and Na/K ATPases in the basal membrane of the pulmonary epithelial cell actively transport Na ϩ out of the cell, creating a transcellular gradient for Na ϩ absorption, mediated through the apical ENaC (4).The ENaC is composed of three homologous subunits, ␣, ␤, and ␥, that together form a functional ion channel (5). In the human lung, ENaC expression has been found along the whole of the respiratory tract, from the nasal epithelium to the alveoli (6, 7).Several important findings point to a critical role for the ENaC in the removal of lung fluid during the later stages of gestation and after birth. Expression of ENaC, especially the ␣ subunit, increases in the respiratory tract with advancing gestational age in humans (8). In the animal model, ENaC expression is further increased by administration of antenatal steroids (9). Transgenic knockout mice with the ␣ENaC gene disrupted die soon after birth from an inability to remove fluid from their lungs (10). ENaC can be effectively blocked by the drug amiloride, which acts as a competitive antagonist to Na ϩ absorption (11). Instillation of amiloride into the lungs of guinea pigs just before their birth results in severe respiratory distress after delivery (12). Animal studies have demonstrated the importance of lung fluid removal on postnatal adaptation (13). Lambs born immediately after removal of half their lung fluid had significantly improved oxygenation and carbon dioxide clearance in the first few hours after birth compared with a control group.The processes that determine the change in ion transport pattern at birth are not f...

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Tracheal fluid in fetal lambs: spontaneous decrease prior to birth

Cited by 126 publications

References 0 publications

Atrial Natriuretic Factor During the Perinatal Period: Equal Depletion in Both Atria'

Atrial Natriuretic Factor During the Perinatal Period: Equal Depletion in Both Atria'

Oxytocin-induced labor augments IL-1β-stimulated lung fluid absorption in fetal guinea pig lungs

Airway Ion Transport on the First Postnatal Day in Infants Delivered Vaginally or by Elective Cesarean Section

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