Developing bronchopulmonary epithelium of the human fetus secretes fluid

1992 ◽  
Vol 262 (3) ◽  
pp. L270-L279 ◽  
Author(s):  
P. B. McCray ◽  
J. D. Bettencourt ◽  
J. Bastacky
Keyword(s):  
Human Fetus ◽  
Chloride Transport ◽  
Fetal Lung ◽  
Fluid Secretion ◽  
Chloride Secretion ◽  
Beta Agonist ◽  
Lung Fluid ◽  
Luminal Area ◽  
Fluid Production ◽  
Human Fetal Lung

We studied human fetal lung tissue in submersion organ culture to determine whether the bronchopulmonary epithelium secretes fluid during development. In this system the acinar tubules continued to grow, secrete fluid, and become progressively dilated. Baseline transepithelial potential differences (psi t) of -0.5 to -11 mV (mean, -3.8 mV, lumen negative, n = 27) were measured with microelectrodes after 3-8 days in culture, suggesting active electrolyte transport. Bumetanide (500 microM), an inhibitor of chloride secretion in other systems, decreased the basal psi t from -5 +/- 1.5 to -3.2 +/- 1.6 (SE) mV (P less than 0.05, n = 6), suggesting that chloride transport contributed to the voltage. Isoproterenol (5 microM) increased the baseline psi t from -5.6 +/- 2.1 to -9.2 +/- 2.5 (SE) mV (P less than 0.05, n = 4). Subsequent addition of bumetanide inhibited the isoproterenol-induced stimulation of the psi t by 20% (P less than 0.05). 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate. (CPT-cAMP, 50 microM) and 3-isobutyl 1-methylxanthine (IBMX, 100 microM) had similar effects, causing an increase in the psi t from -2.2 +/- 0.5 to -8 +/- 1.6 (SE) mV, an effect that was inhibited by the addition of bumetanide (P less than 0.005, n = 6). Both isoproterenol and CPT-cAMP/IBMX produced significant increases in the percentage luminal area of the explants at 12 and 24 h after exposure compared with control. We conclude that 1) the developing bronchopulmonary epithelium (acinar tubules) contributes to lung fluid production in the human fetus, 2) fetal lung fluid secretion is chloride dependent, and 3) chloride secretion and fluid secretion may be stimulated by a beta-agonist and cAMP.

ClC-5: ontogeny of an alternative chloride channel in respiratory epithelia

2002 ◽  
Vol 282 (3) ◽  
pp. L501-L507 ◽  
Author(s):  
Rebecca D. Edmonds ◽  
Ian V. Silva ◽  
William B. Guggino ◽  
Robert B. Butler ◽  
Pamela L. Zeitlin ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Lung Disease ◽  
Chloride Channel ◽  
Chloride Channels ◽  
Chloride Transport ◽  
Premature Death ◽  
Fetal Lung ◽  
Chloride Secretion ◽  
Normal Lung ◽  
Ribonuclease Protection Assay

Chloride transport is critical to many functions of the lung. Molecular defects in the best-known chloride channel, cystic fibrosis transmembrane conductance regulator (CFTR), lead to impaired function of airway defensins, hydration of airway surface fluid, and mucociliary clearance leading to chronic lung disease, and premature death, but do not cause defects in lung development. We examined the expression of one member of the ClC family of volume- and voltage-regulated channels using the ribonuclease protection assay and Western blot analysis in rats. ClC-5 mRNA and protein are most strongly expressed in the fetal lung, and expression is maintained although downregulated postnatally. In addition, using immunocytochemistry, we find that ClC-5 is predominantly expressed along the luminal surface of the airway epithelium, suggesting that ClC-5 may participate in lung chloride secretion. Identifying candidate genes for critical ion transport functions is essential for understanding normal lung morphogenesis and the pathophysiology of several lung diseases. In addition, the manipulation of non-CFTR chloride channels may provide a viable approach for treating cystic fibrosis lung disease.

Inhibition of CLC-2 chloride channel expression interrupts expansion of fetal lung cysts

2004 ◽  
Vol 286 (2) ◽  
pp. L420-L426 ◽  
Author(s):  
Carol J. Blaisdell ◽  
Marcelo M. Morales ◽  
Ana Carolina Oliveira Andrade ◽  
Penelope Bamford ◽  
Michael Wasicko ◽  
...  
Keyword(s):  
Chloride Channel ◽  
Fluid Transport ◽  
Fetal Lung ◽  
Chloride Secretion ◽  
Normal Lung ◽  
Apical Surface ◽  
Lung Cysts ◽  
Lung Fluid ◽  
Lung Morphogenesis ◽  
Channel Expression

Normal lung morphogenesis is dependent on chloride-driven fluid transport. The molecular identity of essential fetal lung chloride channel(s) has not been elucidated. CLC-2 is a chloride channel, which is expressed on the apical surface of the developing respiratory epithelium. CLC-2-like pH-dependent chloride secretion exists in fetal airway cells. We used a 14-day fetal rat lung submersion culture model to examine the role of CLC-2 in lung development. In this model, the excised fetal lung continues to grow, secrete fluid, and become progressively cystic in morphology ( 26 ). We inhibited CLC-2 expression in these explants, using antisense oligonucleotides, and found that lung cyst morphology was disrupted. In addition, transepithelial voltage ( Vt) of lung explants transfected with antisense CLC-2 was inhibited with Vt = -1.5 ± 0.2 mV (means + SE) compared with -3.7 ± 0.3 mV (means + SE) for mock-transfected controls and -3.3 ± 0.3 mV (means + SE) for nonsense oligodeoxynucleotide-transfected controls. This suggests that CLC-2 is important for fetal lung fluid production and that it may play a role in normal lung morphogenesis.

Insulin inhibits beta-adrenergic responses in fetal rabbit lung in explant culture

1992 ◽  
Vol 263 (5) ◽  
pp. L562-L567 ◽  
Author(s):  
D. J. Davis ◽  
J. M. Hickman ◽  
C. A. Lefebvre ◽  
M. E. Lyon
Keyword(s):  
Fetal Lung ◽  
Explant Culture ◽  
Beta Agonist ◽  
Rabbit Lung ◽  
Beta Adrenergic ◽  
Infants Of Diabetic Mothers ◽  
Lung Fluid ◽  
Camp Generation ◽  
Increased Risk ◽  
Diabetic Mothers

Infants of diabetic mothers are at increased risk of a number of problems at birth. Among these problems are increased risks of respiratory distress syndrome and transient tachypnea of the newborn. Because surfactant synthesis, surfactant secretion, and lung fluid resorption are all mediated in part by beta-adrenergic responses, we asked if excess insulin interferes with the beta-adrenergic response cascade in fetal lung. Lungs from fetal rabbits (26 day) were grown in explant culture in hormone-supplemented culture medium. The explants were harvested after 48 h exposure to hormones and processed for determination of beta-adrenergic receptor concentration, guanine nucleotide regulatory proteins (Gs, Gi), beta-agonist stimulated adenosine 3',5'-cyclic monophosphate (cAMP) generation, cAMP-dependent phosphodiesterase activity, and choline incorporation into phosphatidylcholine. Although insulin did not change the concentration of beta-adrenergic receptors, it decreased the ability of isoproterenol to stimulate cAMP generation. Increase in stimulation over basal was similar in explants treated with dexamethasone and dexamethasone plus insulin, but absolute levels of isoproterenol-stimulated cAMP were less in the explants treated with dexamethasone plus insulin. We speculate that insulin inhibition of cAMP generation may be important in the pathogenesis of the respiratory problems of infants of diabetic mothers.

Effects of cAMP, its analogues, and forskolin on lung fluid production by in vitro lung preparations from fetal guinea pigs

1992 ◽  
Vol 70 (3) ◽  
pp. 330-337 ◽  
Author(s):  
Pawel M. Kindler ◽  
Sepideh Ziabakhsh ◽  
Anthony M. Perks
Keyword(s):  
Guinea Pigs ◽  
Fetal Lung ◽  
Dilution Method ◽  
Adenylate Cyclase System ◽  
Dibutyryl Camp ◽  
Lung Fluid ◽  
Fluid Production ◽  
High Doses ◽  
Lung Liquid

Lungs from fetal guinea pigs (62 ± 1 days of gestation) were supported in vitro for 3 h and fluid production was determined by a dye dilution method, based on Blue Dextran 2000. Twenty untreated lungs produced fluid at 1.41 ± 0.22 mL∙kg−1 body weight∙h−1, with no significant changes during later hours. Treatments with analogues of cAMP, cAMP, or forskolin during the middle hour reduced production significantly. Dibutyryl cAMP at 10−3 M produced reabsorption (117.8 ± 13.6% reduction, p < 0.001, n = 10); at 10−4 M it reduced production (77.3 ± 11.0% fall, p < 0.001, n = 10). 8-Bromo-cAMP appeared more effective; at 10−4 M it caused slight reabsorption (109.0 ± 8.9% reduction, p < 0.001, n = 6) and at lower concentrations it decreased production (at 10−6 M, 67.6 ± 9.6% fall, p < 0.001, n = 6; at 10−7 M, 40.0 ± 14.3% fall, p < 0.001, n = 6). At high doses, cAMP itself produced similar effects (at 5 × 10−3 M, 141.6 ± 22.8% reduction, p < 0.001, n = 6); at 10−4 it was ineffective (n = 3). Forskolin at 10−6 M induced the strongest reabsorptions seen (159.1 ± 10.9% reduction, p < 0.001, n = 6); at lower concentrations it reduced production (at 10−8 M, 73.8 ± 5.5% fall, p < 0.001, n = 6; at 10−9 M, 29.2 ± 9.2% fall, p < 0.05, n = 6). These results suggest a possible role for the adenylate cyclase system in the arrest of lung liquid production in the guinea pig around birth.Key words: cAMP, forskolin, fetal lung, lung fluid.

Expression of CFTR and presence of cAMP-mediated fluid secretion in human fetal lung

1992 ◽  
Vol 262 (4) ◽  
pp. L472-L481 ◽  
Author(s):  
P. B. McCray ◽  
W. W. Reenstra ◽  
E. Louie ◽  
J. Johnson ◽  
J. D. Bettencourt ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Lung Tissue ◽  
Light And Electron Microscopy ◽  
Fetal Lung ◽  
Fluid Secretion ◽  
Developmental Expression ◽  
Normal Lung ◽  
Second Trimester ◽  
Significant Change ◽  
Human Fetal Lung

We studied the developmental expression of the cystic fibrosis (CF) gene in human lung tissue from normal and CF-affected fetuses. Two unrelated CF fetuses, both homozygous for the delta F508 deletion, were examined. Cystic fibrosis transmembrane conductance regulator (CFTR) mRNA was present in second-trimester CF lung and in first- and second-trimester normal lung as assessed by amplification of reverse transcribed total RNA with the use of the polymerase chain reaction. CFTR protein was identified by immunoprecipitation in normal second-trimester fetal lung explants. To evaluate possible functional consequences of CF in the fetus, lung tissue explants were grown in submersion organ culture. By light and electron microscopy, the CF fetal lung explants appeared normal. When explants from normal fetal lung were exposed to 8-(4-chlorophenylthio) adenosine 3',-5'cyclic monophosphate (CPT-cAMP), and 3-isobutyl-1-methylxanthine (IBMX) for 24 h, the intraluminal fluid content increased, as assessed by a 40 +/- 4% increase in cross-sectional diameter. In contrast, identically treated CF explants showed no significant change in explant diameter (3 +/- 1.6%). The transepithelial potential (psi t) across fetal lung explants was measured with microelectrodes. In normal second-trimester explants, CPT-cAMP and IBMX caused hyperpolarization of psi t (-0.93 +/- 14 mV to -4.3 +/- 1.2 mV); in contrast, CF fetal lung explants showed no significant change in psi t with CPT-cAMP and IBMX (-0.84 +/- 0.07 mV to -1.21 +/- 0.26 mV). This study confirms the presence of CFTR mRNA and protein in human fetal lung and suggests that although the CF fetal lung appears normal morphologically, there is a defect in cAMP-mediated fluid secretion in the lung of the CF fetus.

pH-regulated chloride secretion in fetal lung epithelia

2000 ◽  
Vol 278 (6) ◽  
pp. L1248-L1255 ◽  
Author(s):  
Carol J. Blaisdell ◽  
Rebecca D. Edmonds ◽  
Xi-Tao Wang ◽  
Sandra Guggino ◽  
Pamela L. Zeitlin
Keyword(s):  
Epithelial Cells ◽  
Short Circuit ◽  
Fetal Lung ◽  
Chloride Secretion ◽  
Lung Epithelial Cells ◽  
Apical Surface ◽  
Ussing Chambers ◽  
Lung Fluid ◽  
Lung Epithelial ◽  
Distal Lung

The fetal lung actively transports chloride across the airway epithelium. ClC-2, a pH-activated chloride channel, is highly expressed in the fetal lung and is located on the apical surface of the developing respiratory epithelium. Our goal was to determine whether acidic pH could stimulate chloride secretion in fetal rat distal lung epithelial cells mounted in Ussing chambers. A series of acidic solutions stimulated equivalent short-circuit current ( I eq) from a baseline of 28 ± 4.8 (pH 7.4) to 70 ± 5 (pH 6.2), 114 ± 12.8 (pH 5.0), and 164 ± 19.2 (pH 3.8) μA/cm2. These changes in I eq were inhibited by 1 mM cadmium chloride and did not result in large changes in [3H]mannitol paracellular flux. Immunofluorescent detection by confocal microscopy revealed that ClC-2 is expressed along the luminal surface of polarized fetal distal lung epithelial cells. These data suggest that the acidic environment of the fetal lung fluid could activate chloride channels contributing to fetal lung fluid production and that the changes in I eqseen in these Ussing studies may be due to stimulation of ClC-2.

Characteristics of fetal lung fluid production

1981 ◽  
Vol 16 (6) ◽  
pp. 943-946 ◽  
Author(s):  
Dennis W. Shermeta ◽  
Irene Oesch
Keyword(s):  
Fetal Lung ◽  
Lung Fluid ◽  
Fluid Production

Fluid production by in vitro lungs from fetal guinea pigs

1990 ◽  
Vol 68 (4) ◽  
pp. 505-513 ◽  
Author(s):  
A. M. Perks ◽  
J. J. Dore ◽  
R. Dyer ◽  
J. Thom ◽  
J. K. Marshall ◽  
...  
Keyword(s):  
Guinea Pigs ◽  
Average Rate ◽  
Fluid Secretion ◽  
Independent Study ◽  
Fluid Composition ◽  
Lung Fluid ◽  
Fluid Production ◽  
Lung Liquid ◽  
Secretion Rates

Lungs from fetal guinea pigs (54–67 days of gestation) were supported in vitro, and lung liquid secretion rates were measured by a dye-dilution technique. The average secretion rate in the first hour was 2.14 ± 0.08 (SE) mL∙kg−1 body weight∙h−1 (0.21 ± 0.01 mL/h) (n = 450); this was comparable to intact preparations. In an independent study of 30 lungs, secretion continued unchanged for 3 h, with no significant change in fluid composition. Between 54 days and term, production appeared to fall in terms of millilitres per kilogram per hour. The following agents were placed in the supporting saline during the middle hour of incubation. (i) Sodium iodoacetate: at 10−4 M this produced a fall in secretion (fall, succeeding hours; 55.4 ± 23.0 and 64.9 ± 17.5%; n = 6); at 10−3 M it stopped secretion (fall, succeeding hours; 87.2 ± 10.3 and 100%, n = 6). (ii) Ouabain: at 10−5 M there was no change in production (n = 6); at 10−4 M, four preparations were unaffected, two reduced production. (iii) Epinephrine (10−7 M) produced a significant fall in production in all cases (n = 6); in four preparations secretion reduced (average fall, 64.4 ± 10.8%); in two preparations there was reabsorption (average rate, −1.03 mL∙kg−1∙h−1). This extends the effect of epinephrine to the guinea pig, and suggests that the in vitro preparation is a useful model for studies of the fetal lung.Key words: fetus, lung fluid, secretion, iodoacetate, epinephrine.

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