Modified method using a somatostatin analogue, octreotide acetate (Sandostatin) to assess in vivo insulin sensitivity

In order to evaluate the steady state plasma glucose (SSPG) method by using a new somatostatin derivative, octreotide acetate (Sandostatin) instead of somatostatin that we had used for the insulin sensitivity test, we examined whether octreotide was able to suppress C-peptide (CPR), glucagon (IRG), and GH to a similar degree to that achieved with somatostatin. A total of 52 studies were performed in 45 essential hypertensive subjects and 7 healthy subjects. Octreotide was given subcutaneously in a does of 50 micrograms or 100 micrograms 10 min before the test (sc 50, sc 100 groups) or intravenously infused over 2 h (10 micrograms in bolus followed by a constant infusion, 50, 100, or 150 micrograms/2 h: i.v. 50, i.v. 100, i.v. 150 groups). In all of the groups the plasma immunoreactive insulin (IRI) concentration increased gradually after insulin injection and reached the steady state plasma insulin (SSPI) level between 40 and 60 microU/ml at 60 min through 120 min. Plasma CPR at 120 min was the most suppressed (by 67% of the basal level in i.v. 150 group during the study period), but on the other hand in both the sc 100 and i.v. 100 groups the plasma CPR concentration at 120 min was suppressed by nearly 40%, but not significantly suppressed in either the sc 50 or the i.v. 50 group. Plasma IRG and GH were strongly suppressed after 60 min in all groups during the study period. Plasma glucose had increased significantly at 30 min and reached the steady state at 90 min through 120 min in hypertensive and healthy subjects. The results indicated that the modified SSPG method with continuous intravenous infusion of Octreotide at 150 micrograms/2 h was adequate for the measurement of insulin sensitivity.