Age-matched series of control and “latent diabetic” children were given intravenous glucose tolerance tests and sera obtained for assay of insulin-like activity (ILA). The rat epididymal fat pad method was used, measuring incorporation of C-14 of glucose-1-C-14 into both CO2 and glycogen. Glycogen yielded the lower results and the greater statistical precision.

ILA was divided into “suppressible” and “nonsuppres-eible” fractions on the basis of inactivation by a guinea pig anti-insulin serum. Extraction with acid-ethanol did not increase the “suppressible” fraction, and added very little useful information to the study.

The chief difference between the two series was the smaller response of “suppressible” ILA after glucose in the “latent diabetics” than in the controls. This difference was most marked (p < .001) at fifteen minutes when the control response was maximal. By contrast, “nonsuppres-sible” ILA was not altered by a glucose load, but the baseline level was higher in the controls (p < .05).

In the fasting state, “suppressible” ILA was higher in the “latent diabetics” than in the controls when CO2 was measured, but this difference was not seen with glycogen.

In each series, the fifteen-minute ILA response depended on the k value for rate of glucose disappearance as determined by simultaneous capillary blood glucose levels. But even when matched for similar k values, this response was greater in the controls than in the “latent diabetics.” In the controls with k values > 2.3, “suppressible” ILA attained fifteen minutes after glucose showed an upward trend with increasing age.

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