Effect of insulin hypoglycemia on the human sigmoid colon

Summary 1. The effect of insulin hypoglycemia on sigmoid activity was studied in 8 normal subjects by the use of small balloons and open-ended catheters. On separate occasions, colonic activity was studied in 4 of these subjects following intravenous glucagon.2. When compared to the preinsulin level of activity, the response to insulin was biphasic, consisting of a depression phase during the 30- to 60-min. period and an excitatory phase during the 150- to 180-min. period. When compared to control (no injection) and placebo (saline) experiments, only the depression phase was significant.3. No difference was observed in the effect of glucagon-free insulin and commercial insulin on colonic activity.4. A positive correlation was observed between blood sugar levels and colonic activity following intravenous insulin.5. Following intravenous glucagon, the number of waves was increased during the 0- to 30-min. period when comparison was made to the pre-glucagon level and to the same time interval in the placebo and insulin studies.The authors wish to acknowledge the invaluable assistance of Drs. Thomas E. Machella and Frank P. Brooks in carrying out this investigation.