Abstract
Insulin and glucagon release in the isolated perfused rat pancreas was measured after
stimulation with tolbutamide. The perfusion medium contained either 5.5 mM of glucose
or was glucose free. During the first ten min of perfusion with tolbutamide, insulin
output rose rapidly while glucagon release was significantly depressed. After a period
of prolonged stimulation glucagon began rising again but did not return to initial
levels. Following destruction of insulin-producing Bcells by streptozotocin, tolbutamide
still caused identical inhibition of glucagon secretion, as in the presence of intact
islets.
A significant inverse relationship between insulin and glucagon output seemed to
be established. Yet, despite the fact that considerably higher insulin levels were
kept in the presence of 5.5 mM glucose in the perfusate, tolbutamide effected about
the same depression of glucagon quantitatively as in the presence of low insulin levels.
Tolbutamide seems to block the glucagon releasing mechanism independent of the functional
state of B-cells.
Key words
Isolated Perfused Pancreas - Tolbutamide Effect - Insulin Secretion - Glucagon Depression
- Streptozotocin Action
1 Presented in part at the 6th Congress of the European Association for the Study of
Diabetes, Warsaw, 1970, and published in abstract form in Diabetologia 6: 636 (1970)
2 Fellow of Alexander von Humboldt Stiftung.
3 Assoc. Prof, of Medicine, University of Colorado Medical Center, and Visiting Prof,
in 1970 at the University of Ulm.
4 Supported by Deutsche Forschungsgemeinschaft, Bad Godesberg (Pf 38/24).
