Evaluation of a 'true' fractional removal rate of glucose in man by bolus and simulated-ramp increase of glucose.

An infusion method designed to produce a gradual ramplike rise in plasma glucose levels in man showed that the observed slope of the ramp was not significantly different from the calculated slope only when both of the following parameters were used: 1. When the glucose disappearance rate coefficient (k) was calculated by an incremental method in which the fasting plasma glucose level was subtracted from each plasma glucose value obtained during a standard rapid intravenous glucose tolerance test. This proved to be superior to a contrasting method in which absolute glucose values are used for the semilogarithmic plot of glucose concentration versus time. 2. When the dilution technic was used to estimate directly the volume distribution of glucose rather than relying on standard reference tables that predict glucose distribution space in man. By using these two parameters obtained during standard intravenous glucose tolerance testing, we have shown that it is possible to calculate the rate of glucose infusion required to achieve successfully in man a ramp of plasma glucose of any desired steepness and to characterize the consequent insulin secretion. This simulated ramp increase of glucose provides a potentially useful tool for investigation of the dynamics of islet-cell function in man.