MODIFIED METHOD USING A SOMATOSTATIN ANALOG, OCTREOTIDE ACETATE (SANDOSTATIN(R)) 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(R )) instead of somatostatin that we had used for the insulin sensitivit y test, we examined whether octreotide was able to suppress C-peptide (CPR), glucagon (IRG), and GH to a similar degree to that achieved wit h somatostatin. A total of 52 studies were performed in 45 essential h ypertensive subjects and 7 healthy subjects. Octreotide was given subc utaneously in a does of 50 mu g or 100 mu g 10 min before the test (sc 50, sc 100 groups) or intravenously infused over 2 h (10 mu g in bolu s followed by a constant infusion, 50, 100, or 150 mu g/2 h: iv 50, iv 100, iv 150 groups). In all of the groups the plasma immunoreactive i nsulin (IRI) concentration increased gradually after insulin injection and reached the steady state plasma insulin (SSPI) level between 40 a nd 60 mu U/ml at 60 min through 120 min. Plasma CPR at 120 min was the most suppressed (by 67% of the basal level in iv 150 group during the study period), but on the other hand in both the sc 100 and iv 100 gr oups the plasma CPR concentration at 120 min was suppressed by nearly 40%, but not significantly suppressed in either the sc 50 or the iv 50 group. Plasma IRG and GH were strongly suppressed after 60 min in all the groups during the study period. Plasma glucose had increased sign ificantly 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 Octre otide at 150 mu g/2 h was adequate for the measurement of insulin sens itivity.