Diabetes
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

This Article
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Nagamatsu, S.
Right arrow Articles by Grodsky, G. M.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Nagamatsu, S.
Right arrow Articles by Grodsky, G. M.
Social Bookmarking
Add to CiteULike   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati  
What's this?

Diabetes, Vol 37, Issue 10 1426-1431, Copyright © 1988 by American Diabetes Association

ARTICLES

Glucose-regulated proinsulin processing in isolated islets from rat pancreas

S Nagamatsu and GM Grodsky
Metabolic Research Unit, University of California, San Francisco 94143.

We demonstrated previously that the conversion rate of proinsulin to insulin in pancreatic islets progressively increased after prolonged prior exposure to glucose (11 mM) and that this effect could be blocked by cycloheximide. This study was designed to characterize further the time course and regulation of the proinsulin conversion process. The effects of prior exposure to glucose on proinsulin conversion were dose dependent (Km, approximately 7 mM glucose) and time dependent, taking approximately 3 h to reach the maximum rate. Glucose added at or after the subsequent [3H]leucine pulse was ineffective. Mannoheptulose, added during a 3-h exposure with glucose (11 mM), prevented glucose-induced activation of the proinsulin conversion process. L-Leucine (20 mM) was as effective as 11 mM glucose in activating conversion, whereas 2-alpha-ketoisocaproic acid (20 mM) or phorbol ester (50 nM) had little effect. Activation of proinsulin conversion by a 24-h exposure to glucose (11 mM) was reversed by a subsequent 3-h prior exposure to cycloheximide. alpha-Amanitin, an inhibitor of mRNA synthesis, did not influence the glucose-induced activation of proinsulin conversion when present during a 3-h exposure to glucose; however, it completely inhibited glucose-stimulated conversion when present during 24 h exposure. Results suggest that activation of the proinsulin conversion process is regulated by glucose metabolism rather than the glucose molecule per se and that other, but not all, secretagogues are effective. Conversion may require prior synthesis of a pool of converting enzyme(s) or other regulatory proteins whose turnover is relatively rapid (approximately 33 h) and whose mRNA is more stable (to 24 h).
Add to CiteULike CiteULike   Add to Del.icio.us Del.icio.us   Add to Digg Digg   Add to Reddit Reddit   Add to Technorati Technorati    What's this?




HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Diabetes Diabetes Care Clinical Diabetes Diabetes Spectrum
Copyright © 1988 by the American Diabetes Association.