ISSN:
1432-0428
Keywords:
Insulinoma
;
IRI content of insulinoma
;
ultrastructural categorization of insulinomas
;
proinsulin content of insulinomas
;
functional defect in insulinomas reduced storage capacity of insulinoma cells
;
non-granular insulin release
;
proinsulin content of human pancreas
;
diazoxide response of insulinomas
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary Thirty human insulinomas have been investigated histologically and their immunoreactive insulin (IRI) content estimated. In most cases immunohistological and ultrastructural studies were also performed and the percentage of proinsulin-like components (PLC) in the tumour determined. Except for 1 case the IRI concentration in the tumours was lower (0.01–89.0 U/g) than in the islet tissue. Histologically, immunohistologically and ultrastructurally a variable number of tumour cells contained few and often no beta-granules, indicating a decreased storage capacity for insulin. This defective storage capacity seems to be the major functional abnormality of insulinoma cells. Ultrastructurally four types of insulinoma can be distinguished. The ultra-structural diagnosis of an insulinoma can only be made in type I (typical beta-granules, 13 cases) and type II (typical and atypical granules, 7 cases) but not in type III (atypical granules only, 4 cases) and type IV (virtually agranular, 4 cases). The type IV tumours had the lowest IRI concentration and did not respond to diazoxide treatment. The IRI concentration of the uninvolved pancreas of 19 patients was 2.0±0.2 U/g and in the range of non-diabetic adults. — The percentage PLC in 19 insulinomas was higher (5.3–22%) than in the pancreas of human adults with and without insulinoma (1.7–4.8%). The percentage of PLC in the serum of patients with insulinoma was always higher than in their tumours (33–61%). It is suggested that the higher PLC levels found in the tumour and serum of insulinoma patients are the consequence of the reduced storage capacity of the tumour cells resulting in a rapid passage through the granular route or even a non-granular release of newly synthesized insulin.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01219786
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