Synthesis and release of proinsulin and insulin by isolated rat islets of Langerhans

Tomio Tanese; Norman R. Lazarus; Sevim Devrim; Lillian Recant

doi:10.1172/JCI106357

^{Veterans Administration Hospital, Washington, D. C. 20422}

^{Georgetown University School of Medicine, Washington, D. C. 20007}

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^{Veterans Administration Hospital, Washington, D. C. 20422}

^{Georgetown University School of Medicine, Washington, D. C. 20007}

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^{Veterans Administration Hospital, Washington, D. C. 20422}

^{Georgetown University School of Medicine, Washington, D. C. 20007}

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^{Veterans Administration Hospital, Washington, D. C. 20422}

^{Georgetown University School of Medicine, Washington, D. C. 20007}

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Published in Volume 49, Issue 7 on July 1, 1970
J Clin Invest. 1970;49(7):1394–1404. https://doi.org/10.1172/JCI106357.
© 1970 The American Society for Clinical Investigation

Published July 1, 1970 - Version history

Isolated rat islets of Langerhans were incubated for 60, 120, and 180 min and the incorporation of leucine-³H into proinsulin and insulin moieties was followed. Synthesis and release of these hormones could be followed by separate extractions of islets and incubation media.

Release of newly synthesized proinsulin and insulin occurred under the following conditions: (a) incubation for greater than 60 min; (b) glucose concentrations above 5.3 mmoles/liter; (c) incubation with 5 mM dibutyryl cyclic AMP or theophylline in 5.3 mM glucose (potentiated by 16 mM glucose); and (d) incubation with 5 mM tolbutamide and 16 mM glucose.

Synthesis of proinsulin and insulin was enhanced by time of incubation, high glucose concentrations, by dibutyryl cyclic AMP or theophylline, and by tolbutamide only at 16 mM glucose. Synthesis was totally inhibited by tolbutamide at 5.3 mM glucose.

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