抄録
Brown et al. isolated a new gastrointestinal active substance, motilin. However, there are still some discrepancies in motilin research. Recently Yanaihara et al. have synthesized motilin and succeeded in making antisera raised in guinea pig and rabbit against synthetic motilin. So we measured plasma motilin with dextran-charcoal radioimmunoassay method using antiserum GP1103. Since it is important to elucidate the significance of pathophysiological role of motilin, we studied in the present experiment the relationship between plasma motilin level and gastric motor activity, and have measured plasma motilin levels in normal subjects and patients with diabetes mellitus, hyperthyroidism and chronic liver diseases. In seven healthy conscious dogs plasma motilin level was measured while the gastric contractile activity was recorded by means of a chronically implanted force transducer. When the gastric contractile activity was in the interdigestive state, plasma motilin level was always elevated in all dogs. The high plasma concentration of motilin was lowered by ingestion of food and this low level of motilin lasted as long as the gastric motor activity was in the digestive pattern. However, plasma motilin level returned to the high level again by the time when the gastric motor activity was in the interdigestive state. Furthermore, we observed that plasma motilin concentration fluctuates in complete association with gastric contractions during the interdigestive state. In human study the similar findings wereobtained. Plasma motilin concentration during the prolonged fasting also fluctuated at approximately 100 min intervals and the episodic secretions appeared to parallel the occurence of the interdigestive gastric contraction. Besides, in 8 normal subjects we studied the change of plasma motilin levels before and after meals. In fasting plasma motilin fluctuated as described above, and plasma motilin rised transiently within 30 min after meal and then decreased gradually from 30 min after meal. After administration of either 50g of glucose orally or 25g of glucose intravenously plasma motilin decreased gradually in normal subjects. In normal subjects, following the intravenous administration of 0.1U/Kg regular insulin, plasma motilin decreased in accordance with diminished blood glucose. Fasting plasma motilin levels in normal subjects were widely distributed ranging from less than 50pg/ml to 540pg/ml, with the mean of 224±36 (SE) pg/ml. In hyperthyroid patients fasting plasma motilin was 314±64pg/ml, which was not different from that of normal subjects. Patients with diabetes mellitus and with chronic liver disease had fasting plasma motilin levels of 505±89pg/ml and 391±71pg/ml, respectively, both of which were significantly higher than those in normal subjects (p<0.05). Following 50g oral glucose loading, plasma motilin levels decreased in all three groups as well as normal subjects. These results suggest that motilin is released in the fasting state and plays an important role in the gastric activity: especially interdigestive motor activity of the stomach may be controlled by plasma motilin concentration in the dog and man. We have proposed therefore the “interdigestive hormone” for this newly identified gut hormone.
