ABSTRACT
The insulin secretory response in the rat to intravenous glucose was found to be greatly impaired by fasting for three days, whereas that to orally administered glucose was not significantly affected. Rats fasted for two days were given either protein or starch pellets for six hours, and then fasted for a further eighteen hours before the intravenous glucose test. The protein pre-feeding failed to affect significantly the subsequent insulin secretory response to intravenous glucose, whereas starch prefeeding greatly enhanced it. It is suggested that intestinal hormones released by glucose ingestion may exert not only an acute effect on insulin release, but also a 'priming' effect on the insulin release mechanism of the β cell, which enables it to respond to the subsequent stimulus of glucose alone.