Translations:Insulin/67/en
Extraction and purification
In October 1920, Canadian Frederick Banting concluded that the digestive secretions that Minkowski had originally studied were breaking down the islet secretion, thereby making it impossible to extract successfully. A surgeon by training, Banting knew that blockages of the pancreatic duct would lead most of the pancreas to atrophy, while leaving the islets of Langerhans intact. He reasoned that a relatively pure extract could be made from the islets once most of the rest of the pancreas was gone. He jotted a note to himself: "Ligate pancreatic ducts of dog. Keep dogs alive till acini degenerate leaving Islets. Try to isolate the internal secretion of these + relieve glycosurea[sic]."
In the spring of 1921, Banting traveled to Toronto to explain his idea to John Macleod, Professor of Physiology at the University of Toronto. Macleod was initially skeptical, since Banting had no background in research and was not familiar with the latest literature, but he agreed to provide lab space for Banting to test out his ideas. Macleod also arranged for two undergraduates to be Banting's lab assistants that summer, but Banting required only one lab assistant. Charles Best and Clark Noble flipped a coin; Best won the coin toss and took the first shift. This proved unfortunate for Noble, as Banting kept Best for the entire summer and eventually shared half his Nobel Prize money and credit for the discovery with Best. On 30 July 1921, Banting and Best successfully isolated an extract ("isletin") from the islets of a duct-tied dog and injected it into a diabetic dog, finding that the extract reduced its blood sugar by 40% in 1 hour.