Donald P. Grettie

Plasma Insulin and Glucose Responses of Healthy Subjects to Varying Glucose Loads During Three-hour Oral Glucose Tolerance Tests

The plasma glucose and plasma immunoreactive insulin concentrations of twelve healthy, nonobese, adult subjects were compared following administration of oral glucose loads of 50, 75 and 100 gm., and 1.75 gm./kg. body weight. The time of occurrence and the magnitude of maximal plasma glucose and insulin concentrations were unaffected by the 25 gm. increases in glucose load. The 50 gm. glucose load gave the smallest plasma glucose response during the three-hour tests and this response was statistically distinguishable from the plasma glucose responses due to the 100 gm. and 1.75 gm./kg. loads (p < 0.05). The plasma glucose responses due to the other loads did not differ from each other. Insulin responses, estimated by either summing allthe plasma insulin values or by measuring the areas under the curves, increased approximately 35 per cent with the first 25 gm. glucose load increment (50 to 75 gm.) and 27 per cent with the second 25 gm. load increment (75 to 100 gm.) during the three-hour study. The differences in insulinresponses between the 50 gm. load and the 100 gm. or 1.75 gm./kg. loads were highly significant (p < 0.01) while the difference between the insulin responses following the 75 gm. and 1.75 gm./kg. loads had lower significance (p < 0.05). Differences in insulin responses of the other loads were not significant. Increases in glucose loads above 120 gm. did not further increase the insulin response. This provides evidence that maximal insulin responses provoked by an oral glycemic stimulus alone in subjects are achieved with 100 gm. A wide range was observed in the plasma insulin concentrations among these healthy individuals for any given load, at any one time, and was probably due to biological variation. The fact that incremental changes in glucose load particularly influenced plasma glucose and insulin concentrations relatively late in the glucose tolerance tests, and that mean insulin peakconcentrations did not differ, indicates that increasing glucose load results in a more prolongedinsulinogenic stimulus rather than the acute release of greater quantities of insulin relatively abruptly. These studies provide evidence that the response associated with increasing glucose load is to some extent a function of the quantity of glucose ingested, and that the significant increases in insulin response commonly occur in association with concurrent alterations in plasma glucose concentrations. The results also indicate that the 50 gm. glucose load results in a different plasma glucose response than does the 100 gm. and 1.75 gm./kg. loads and consequently requires different criteria for interpretation of glucose tolerance testing.

Polyamine levels in normal human serum. Comparison of analytical methods.

Abstract A comparison of levels of the polyamines, putrescine, spermidine and spermine, in individual and pooled normal human serum, as determined by three independent methods, high pressure cation-exchange chromatography (HPCC), radioimmunoassay (RIA) and gas chromatography-mass spectrometry (GC-MS), has been made. Generally good correlations were found for values derived by the three different methods.

Effect of diazoxide in plasma glucose and insulin concentrations after acute glycemic stimulation and intravenous tolbutamide

Abstract Five healthy young subjects were subjected to glucose tolerance and tolbutamide tests before and after diazoxide administration. The glucose tolerance tests were made after two challenges with 100 g of glucose. A 5-day treatment with diazoxide (100 mg t.i.d.) lowered the plasma insulin response consistently throughout the second glucose challenge, but did not lower the plasma insulin in response to the tolbutamide challenge. Since tolbutamide stimulates a normal insulin release after diazoxide administration, it appears that the diazoxide did not impair the synthesis and storage of insulin, but that diazoxide interferes with the release of insulin during the glucose challenge. While diazoxide caused a decreased plasma insulin concentration during the glucose challenge, the plasma glucose concentration was not increased in four of the five subjects. The results with normal subjects are in contrast with our observations on an insulinoma patient in whom insulin release was enhanced by diazoxide treatment.

Insulin values of normal pancreatic and pancreatic adenomas tissue extracts in children

Abstract Tissues of four pancreatic adenomas of children with clinical hyper-insulinemia and relative hyperinsulinemia, and normal pancreatic tissue were studied. Tissues were extracted and immunoreactive insulin levels measured per gram of dry tissue. Comparisons of findings in two newborn babies with inverted rate glucose/insulin and two children of 11 and 14 yr of age with hyper-insulinemia are reported. Results indicate relative comparable insulin values in adenoma pancreatic tissue in both age groups per gram of tissue, although larger amounts of circulating immunoreactive insulin were found in older children with true hyperinsulinemia. High insulin concentrations were found in one case. These high levels may be related to the severity or type of cell adenoma.

Practical considerations in angiotensin II antibody production

Abstract When cost considerations are paramount, one immunization with angiotensin II-rabbit serum albumin immunogen into multiple sites in rabbits suffices to produce high-titer antisera which are clinically useful for radioimmunoassays. Although sustained antibody responses may occur after one or two immunizations with an angiotensin II-poly- l -lysine immunogen, titers are impractically low for clinical work.