Physiological Studies on Motor Activity of Gastrointestinal Tract in Experimental Diabetic rats

In order to elucidate the physiological mechanisms of diabetic gastrointestinal disorders, isolated gastrointestinal segments of streptozotocin diabetic rats were studied in vitro from the following viewpoint, i. e. , the size, motor activities, passive physical properties, drug-induced contractility and transmitter contents. 1) Diabetic rats had longer small and large intestine than normal. Wet weight of the diabetic duodenum, jejunum, ileum, colon and caecumu was heavier than that of normal. Stomach weight was similar between diabetic and normal rats. 2) Motor activities were examined by recording the changes in frequency and amplitude of spontaneous intraluminal pressure of isolated preparations, as well as those in electromyographs with suction electrodes. Frequency of the diabetic upper intestine, especially of the duodenum, was significantly lower than that of normal. Amplitude of intraluminal pressure in the diabetic jejunum and caecum was smaller than that of normal. These results suggested the pacemaker disorders in diabetic preparations. 3) Acetylcholine and substance P induced-contractility of the diabetc duodenum, jejunum and ileum was smaller than that of normal, both in longitudinal and circular muscle preparations. However, colonic responsibility to acetylcholine and substance P was similar between diabetic and normal preparations. 4) Substance P and somatostatin contents in gastrointestinal tract were determined by radioimmunoassay. Substance P and somatostatin content per wet weight was increased in the diabetic corpus of stomach. Substance P was decreased in the ileum and caecum and somatostatin was decreased in the caecum. 5) Passive mechanical properties were compared by recording pressure-volume relationships of the isolated gastrointestinal tracts by infusing Tyrode's solution into them. Maximal volume infused was larger in diabetic than in normal preparations even after corrected for length and wet weight. Therefore, compliance or distensibility was higher in diabetic than in normal preparations. In conclusion, disorders of diabetic gastrointestinal tract were suggested to be due to pacemaker disorders, higher compliance, decreased drug-responsibility and transmitter content