Biosynthesis of insulin

Humbel, RenéE.

doi:10.1016/0002-9343(66)90147-1

Cited by 9 publications

(1 citation statement)

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“…This was particularly well illustrated by several days culture in the presence of aIt-leueine, which produced a specific activity about 100 times higher than that obtained during 3 hrs incubation of non-cultured islets. This degree of labelling would be theoretically sufficient for the use of such insulin in biological research [41]. Although the available amounts will of necessity be small it would be interesting to study biosynthetically labelled, homologous insulin with regard to its affinity for antibodies or its metabolism both in vivo and in vitro.…”

Section: Discussionmentioning

confidence: 99%

Effects of glucose on the ultrastructure and insulin biosynthesis of isolated mouse pancreatic islets maintained in tissue culture

1974

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Summary. Isolated mouse pancreatic islets were mainrained in tissue culture for up to 12 days in glucose concentrations varying between 3.3 and 28 raM. A satisfactory ultrastruetural preservation of the islet cells was found irrespective of the glucose concentration of the culture medium. While the B-cells of islets cultured in the lower glucose concentration showed slight degranulation, there was extensive degranulation and increased amounts of rough-surfaced endoplasmic retieulum after culture in the higher glucose concentration. The immunoreactive insulin content of islets cultured at 28 mM glucose was markedly decreased and the insulin secretion during the culture period was much higher than that of islets cultured at 3.3 mM glucose. The insulin biosynthesis, as reflected in the incorporation of 3I-I-leucine into gel chromategraphed extracts of acid-ethanol soluble islet proteins, was studied either during the culture period or at the end of a 6-day culture in short-term incubations lasting for 90 or 180 rain. The results consistently showed tlhat the biosynthesis of insulin proceeded at a high rate and remained regulated by glucose throughout the culture period. The eontinfious addition of newly synthesized and labelled insulin to the small intracellular insulin pool of the high-glucose cultured B-cells produced a very high specific radioactivity of the insulin.Key words : Tissue culture, pancrea tic islets, degranulation, endoplasraie reticulum, insulin content, insulin release, insulin degradation, insulin biosynthesis.Although the responses of the B-cell to an acute glucose challenge have been studied in great detail there is still little known about the long-term reactions of these cells to an increased extraeellular glucose coneentration. Thus, it is unclear whether the deficient insulin response to glucose and the diminished insulin reserves in diabetes mellitus are caused by a primary dysfunction of the cells or secondary functional exhaustion due to the hyperglycemic state. The experimental approach to this problem has been difficult mainly due to the lack of suitable techniques for long-term studies of iso]ated B-cells in a system separate from all the complex influences which occur in rive. In the present study a recently developed technique for in vitro culture of intact isolated islets [1] has been utilized in an attempt to overcome these difficulties. The insulin content and the biosynthesis of insulin have been analysed in mouse pancreatic islets maintained in culture at widely different glucose concentrations. In addition, the insulin release to the culture medium and the glucose-dependent variations of the ultrastructure of the cultured ]3-cells have been evaluated. Materials and Methods A. Tissue Culture TechniqueMale NMI~I mice (Anticimex AB, Stockholm, Sweden) weighing 30--35 g were starved over-night before the experiments. Isolated islets were obtained by digestion of the pancreas with collagenase (Worthington Biochemical * Presented in part at the Congress of the European Association f...

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Section: Discussionmentioning

confidence: 99%