Studies on the secretion of newly synthesized proinsulin and insulin from isolated rat islets of langerhans

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Abstract

Islets of Langerhans isolated from rat pancreas were incubated at 37°C(95% O2/5% CO2) in buffered medium containing 1.0 mg/ml glucose and leucine 3H for 1 hr (1st hr), washed, and incubated for an additional hr (2nd hr) in low glucose medium (0.5-1.0 mg/ml) containing unlabeled leucine. A portion of the islets was then extracted with acid-ethanol and the remainder were transferred to medium containing 3.0 mg/ml glucose and incubated for 2 hr (3rd and 4th hr) at 37°C. The medium was exchanged at 30-min intervals and portions of the islets were extracted at the 3rd and 4th hr. The total amounts and specific activities of the proinsulin and insulin in the islet extracts and medium samples were determined after fractionation on Biogel P-30 columns in 3 M acetic acid.

Authors

Hiroyuki Sando, Jo Borg, Donald F. Steiner