Diabetes, Vol 29, Issue 5 335-340, Copyright © 1980 by American Diabetes Association
Potentiation of insulin secretion to nonglucose stimuli in normal man by tolbutamide
MA Pfeifer, JB Halter, R Graf and D Porte
To determine how sulfonylureas affect beta cell function, insulin release
in response to isoproterenol and arginine was assessed in 32 normal
subjects before and during a tolbutamide infusion. When the plasma glucose
was allowed to decrease during tolbutamide, the acute insulin response
(AIR) to isoproterenol was not changed (delta AIR = 4 +/- 8 MicroU/ml, mean
+/- SEM, n = 8,p = NS) and was enhanced slightly for arginine (delta AIR =
+61 +/- 26 microU/ml, n = 6, p less than 0.05). When plasma glucose levels
were maintained by means of a concomitant variable glucose infusion during
tolbutamide, the insulin responses to both isoproterenol and arginine were
enhanced (isoproterenol: delta AIR = +55 +/- 15 microU/ml, n = 6, p less
than 0.001; arginine: delta AIR = +137 +/- 34 microU/ml, n = 8, p less than
0.001). Regression analysis demonstrated a linear relationship between
change in the prestimulus glucose level and the change in the AIR to
isoproterenol during tolbutamide (r = 0.66, n = 14, p less than 0.02).
Since the slope of his relationship is not significantly different from a
similar relationship in the absence of tolbutamide, the potentiating effect
of tolbutamide is an amplification of an established physiologic
relationship. We conclude that tolbutamide augments the insulin response to
nonglucose stimuli. However, this potentiating effect of tolbutamide may be
masked by a decrease in the prestimulus glucose level.