Frederick Banting's actual great idea: The role of fetal bovine islets in the discovery of insulin.

BACKGROUND

Frederick Banting approached Toronto physiology professor JJR Macleod with a way to prevent pancreatic trypsin from destroying the pancreas' internal secretion. Banting proposed to induce exocrine atrophy by ligating canine pancreatic ducts and to use extracts of islet-rich residua to treat pancreatectomized dogs. His next plan was to make extracts from fetal pancreas, which he had read was islet-rich and lacked exocrine tissue capable of making trypsin; this work has not been historically evaluated.

METHODS

Banting's fetal calf pancreas story is told using primary and secondary historical sources and then critically examined using both historical and recent data on species phylogeny, islet ontogeny, fetal/neonatal islet culture/transplantation, etc. Results/Discussion: Only ruminants develop dual islets populations sequentially; fetal calf pancreata, at the gestational ages Banting used, possess numerous insulin-rich giant peri-lobular islets, which credibly explain the potency of his fetal calf insulin extract. Use of non-ruminant fetal pancreata would have failed.