Insulin and C-peptide (proinsulin) packaging: a quantitative immunocytochemical approach.
C-peptide and insulin antigenic sites in rat pancreatic beta cells were both labeled by the protein A and immunogold techniques. Gold bead density in the secretory granules was correlated with granule size distribution. Our results demonstrate that the distribution patterns of antigenic sites for C-peptide (which also represents proinsulin sites) and insulin are similar when granule size distribution is correlated to the density of antigenic sites. It was found that the ratio of C-peptide to insulin in granules is independent of granule size. Examination of frequency histograms by a Kolmogorov-Smirnov analysis excluded the possibility that the antigenic sites of C-peptide and insulin are distributed in the same manner. Mean gold bead density for insulin antigen (97 +/- 24) was slightly higher than C-peptide density (64 +/- 18). The efficiency of labeling was found to be very low; less than 0.1% of the theoretically estimated antigenic sites were labeled.
Hammel
I
I
Department of Pathology, Sackler School of Medicine, Tel Aviv, Israel.
Kalina
M
M
D000818:Animals; D002096:C-Peptide / Q000032:analysis* / Q000276:immunology; D003594:Cytoplasmic Granules / Q000032:analysis; D006046:Gold; D007150:Immunohistochemistry; D007328:Insulin / Q000032:analysis* / Q000276:immunology; D007515:Islets of Langerhans / Q000032:analysis* / Q000648:ultrastructure; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains
D002096:C-Peptide; D007328:Insulin; D006046:Gold