Document Detail


Glucocorticoid regulation of chloroquine nonsensitive insulin degradation in cultured fetal rat hepatocytes.
MedLine Citation:
PMID:  2687268     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The influence of cortisol and other culture conditions on insulin degradation by the chloroquine-sensitive pathway and the chloroquine-nonsensitive pathway (CNP) was investigated in fetal rat hepatocytes during 3 days of culture. The proportions of the chloroquine nonsensitive release of 125I-insulin degradation products into the conditioned medium/h increased from the 1st to the 3rd day of culture, i.e. from 19 to 50% by cells grown in the presence of cortisol and from 17 to 82% by those grown in the absence of cortisol. Replacement of the conditioned medium with the respective fresh medium dramatically enhanced cellular insulin degradation by CNP, i.e. from 22 to 58%, and 19 to 85% in cells grown for 2 days in the presence and absence of cortisol, respectively. Thus, the conditioned medium contained some factor(s) that inhibited CNP. Therefore, we used the inhibited insulin and alpha-casein degradation by papain in vitro as an assay to investigate the nature of the putative anti-(insulin) protease. Cycloheximide completely prevented the appearance of anti-papain activity in the medium. Conditioned medium obtained from cells grown in the presence of cortisol contained about 2-fold more anti-papain activity than the medium that was obtained in the absence of the steroid. The release of anti-papain activity also declined with time from 1 to 3 days of culture and showed an inverse relationship with the magnitude of cellular insulin degradation by CNP. The inhibition of papain-mediated insulin degradation by the anti-(insulin) protease was noncompetitive. The anti-(insulin) protease was nondialyzable (up to the 10-kDa exclusion limit) and inactivated by heat treatment at 50 degrees C for 30 min. These results suggest that fetal hepatocytes synthesize and secrete a glucocorticoid-regulated heat-labile low molecular mass (less than 25 kDa) anti-(insulin) protease, which may contribute to the suppression of insulin degradation caused by the enzymes involved in CNP.
Authors:
M Ali; C Plas
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  264     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  1989 Dec 
Date Detail:
Created Date:  1990-01-19     Completed Date:  1990-01-19     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  20992-7     Citation Subset:  IM    
Affiliation:
Laboratoire Interactions Cellulaires, U.E.R. Odontologie, Université Paris, France.
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MeSH Terms
Descriptor/Qualifier:
Animals
Cells, Cultured
Chloroquine / pharmacology*
Culture Media
Fetus
Hydrocortisone / pharmacology*
Insulin / metabolism*
Liver / drug effects,  metabolism*
Papain / metabolism
Rats
Chemical
Reg. No./Substance:
0/Culture Media; 11061-68-0/Insulin; 50-23-7/Hydrocortisone; 54-05-7/Chloroquine; EC 3.4.22.2/Papain

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