The biosynthesis of glucagon in perfused rat pancreas |
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Authors: | O'connor K J Gay A Lazarus N R |
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Affiliation: | Diabetes Research Unit, The Wellcome Foundation, Temple Hill, Dartford, Kent, U.K. |
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Abstract: | The biosynthesis of glucagon was studied by using the recirculated, isolated perfused rat pancreas. [3H]Tryptophan was initially incorporated into acid–ethanol-extractable protein, which on gel filtration was eluted with a molecular weight of about 9000 and contained a small amount of glucagon immunoreactivity. With longer incubation [3H]tryptophan incorporation into a second peak was obtained in an identical position with that of the majority of rat glucagon immunoreactivity. This peak of labelled protein exhibited migration characteristics on polyacrylamide-gel electrophoresis identical with those of rat glucagon and was identified as newly synthesized glucagon by demonstration of specific binding and dissociation behaviour with glucagon antibodies. The incorporation of [3H]tryptophan into acid–ethanol-extractable protein was inhibited by cycloheximide. High concentrations of glucose increased [3H]tryptophan incorporation into high-molecular-weight protein but decreased incorporation into proteins smaller than cytochrome c. The pattern of [3H]leucine incorporation into protein was similar to that of [3H]tryptophan. |
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