Document Detail


Actin depolymerization is developmentally regulated in rat type II cells exposed to terbutaline.
MedLine Citation:
PMID:  9029633     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The type II alveolar epithelial cell synthesizes and secretes pulmonary surfactant. Terbutaline enhances phospholipid release from adult and fetal type II cells. Our hypothesis is that the actin network of microfilaments regulates the secretory activity of the type II cell. To examine the developmental regulation of the changes in actin subfractions associated with secretory activity, cultures of type II cells derived from adult and 19-d fetal rat lung were incubated with or without 10 microM terbutaline for 1, 30, and 60 min. Dose-response effects of terbutaline were examined in adult type II cells. Effects of phorbol ester were also examined Globular (G-actin) and filamentous (F-actin) fractions were extracted from the cells and analyzed separately. Specified cellular equivalent volumes of each subfraction were analyzed by Western blotting, visualized by a color reaction, and quantified by densitometry. There was a decrease in the cytoskeletal F-actin pool along with an increase in the G-actin fraction within I min in adult type II cells exposed to terbutaline, indicating that depolymerization of F-actin occurs. Values returned to control levels by 60 min. In contrast, the decrease in F-actin, with a concomitant increase in G-actin, was maximal at 60 min in fetal cells exposed to terbutaline. There was a dose-dependent increase in actin depolymerization with maximal effects at 10 microM terbutaline. Phorbol ester also caused an increase in actin depolymerization. Depolymerization of the actin microfilament network may regulate transport and exocytosis of lamellar bodies in type II cells. We speculate that there is an early secretory mechanism that involves depolymerization of actin microfilaments and a late, actin-independent secretory mechanism present in adult type II cells. The timing of the response of the actin-dependent pathway is developmentally regulated. This may explain the developmental differences in the secretion of surfactant that we have previously shown.
Authors:
V Bhandari; H Lu; J Pachter; M J Kresch
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Pediatric research     Volume:  41     ISSN:  0031-3998     ISO Abbreviation:  Pediatr. Res.     Publication Date:  1997 Feb 
Date Detail:
Created Date:  1997-05-08     Completed Date:  1997-05-08     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0100714     Medline TA:  Pediatr Res     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  166-71     Citation Subset:  IM    
Affiliation:
Department of Pediatrics, University of Connecticut School of Medicine, Farmington 06030-2203, USA.
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MeSH Terms
Descriptor/Qualifier:
Actins / chemistry*
Animals
Biopolymers
Drug Evaluation, Preclinical
Lung / cytology,  drug effects*,  embryology
Pulmonary Surfactants / secretion*
Rats
Rats, Sprague-Dawley
Secretory Rate / drug effects
Terbutaline / therapeutic use*
Chemical
Reg. No./Substance:
0/Actins; 0/Biopolymers; 0/Pulmonary Surfactants; 23031-25-6/Terbutaline

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