Increase of Insulin Concentration in Maturity-Onset Diabetics by Phentolamine (Regitine^®) Infusion

Abstract

It was investigated whether the deficient insulin response in maturity-onset diabetics is determined by monoaminemediated mechanisms.

The material comprised 11 maturity-onset diabetics and 10 non-diabetics as a control group, all non-obese. The tests were carried out on 2 consecutive days, by IV GTT on the first day and IV GTT combined with IV infusion of the α-receptor blocker phentolamine (Regitine^®) 0.5 mg/min on the second day. Serum glucose and serum insulin concentrations were determined.

In the non-diabetic group no increase in serum insulin was found on phentolamine infusion alone, whereas the insulin response after IV injection of glucose was potentiated by phentolamine. In the diabetic group, on the other hand, a statistically significant increase (p < 0.001) in serum insulin was found when phentolamine was given without glucose. During an IV GTT the diabetic group showed a slight and delayed insulin response as usual. This response was potentiated, but not normalized, by phentolamine.

It is concluded that a monoamine-mediated mechanism may play a role in the sluggish insulin release after glucose tolerance tests in maturity-onset diabetics.

Key words

c-3'5' AMP - Phentolamine (Regitine^®) - Maturity-Onset Diabetes - Serum Insulin Level - IV GTT - Monoamine-Mediated Mechanism