In:
Diabetes, American Diabetes Association, Vol. 42, No. 6 ( 1993-06-01), p. 933-936
Abstract:
Islets isolated from human cadaver pancreas were pulse-labeled (10 min with [3H]leucine) and then incubated for a 180-min chase. Islets and chase medium were collected every 15 min and analyzed by reversed-phase HPLC to quantify the percentage of radioactively labeled proinsulin, conversion intermediates, and fully processed insulin. Release of proinsulin-related labeled products into the chase medium was & lt; 10% of total. Whereas 50% of labeled proinsulin had been lost by conversion within 45 min, fully processed insulin only appeared with a half-time of 100 min. This discrepancy is attributable to accumulation of radioactive conversion intermediates. Des 64.65 split proinsulin was a minor component, reaching a maximum of 5.2 ± 1.7% (n = 4) at 60 min of chase. By contrast, des 31.32 split proinsulin—and a truncated form lacking the first three residues of C-peptide—rose progressively to 29.3 ± 1.4% by 75 min, and declined thereafter. The accumulation of des 31.32 split proinsulin rather than the des 64.65 split form during the conversion of human proinsulin reflects slower conversion at the C-peptide/A-chain than at the B-chain/C-peptide junction, and is consistent with the appearance of this particular conversion intermediate in the circulation.
Type of Medium:
Online Resource
ISSN:
0012-1797
,
1939-327X
DOI:
10.2337/diab.42.6.933
Language:
English
Publisher:
American Diabetes Association
Publication Date:
1993
detail.hit.zdb_id:
1501252-9
