Особливості періодичної активності шлунка за умов дисбалансу NO-ергічної системи

Abstract

Nitric oxide is the main inhibitory mediator of the gastrointestinal smooth muscles’ relaxation which stimulates duodenal mucus and bicarbonate secretion. More recent studies have demonstrated that NO also protected the gastrointestinal tract by inhibiting gastric acid secretion. In this study we investigated gastric secretory and motor activity considering the NO imbalance condition. The experiments were carried out on male white laboratory rats (200–230 g). The control group was treated with 0.9% NaCl solution. The injections of NO donator (1.5 mg/kg of 0.1% (Sigma-Aldrich) sodium nitroprusside solution) were made in the second and the third groups during 6 and 12 days. The fourth and the fifth group were treated with NO synthesis inhibitor (40 mg/kg of 1% solution (Sigma-Aldrich) Nω-nitro-L-arginine) during 6 and 12 days respectively. Recording of gastric myoelectric activity (GMA) and gastric juice collection were carried out under anesthesia (ketamine, 110 mg/kg). Next, its volume, pH, glycoprotein and pepsin were measured. Within 6-days stimulation of NO excess decreased gastric juice volume by 47% and increased pH compared to control samples. Pepsin level increased by 62% and glycoprotein level decreased by 68% compared to the checkpoint. After 6 days of L-NNA injections we observed the increase of gastric juice secretion volume (78%) and pH level, however, pepsin concentration remained unchanged. Glycoprotein level increased by 21% compared to control samples. After 12 day NO synthesis inhibitor injections gastric secretion volume increased by 85%. Gastric juice pH level was 200% higher than the control value and exceeded gastric juice pH level (62%) in the third group. In addition, pepsin level tended to decrease when NO deficiency simulation was prolonged. Glycoprotein level decreased by 41% compared to control samples and by 51% compared to the third group. Pepsin level decreased after 12 day NO-inhibitor injections as gastric juice pH level increased. After 12 day Na-nitroprusside treatment, gastric myoelectric index decreased by 42% compared to the checkpoint. The type of contractions is typical to the I phase of the basic electrical rhythm (BER). Also, retrograde entrainment of duodenal rhythm took place. After 6 day L-NNA injections, GMA was the same as the period between II and III phase of BER. Late second and early third phases predominated, while the I phase wasn’t detected during the recording. In case of long-lasting disorder of NO-system, motor index value significantly differed from the control group samples and depended on the duration of NO-synthase blocking. On the 6th day of L-NNA treatment, the level of motor index increased 1.5 times. GMA phases could be identified only on the basis of motor index values. Stomach’s own rhythms disappeared and duodenogastric reflux resulted in domination of duodenal rhythms. After 12 day L-NNA injections, duration of the II and III phases increased while the I phase of gastric BER disappeared; gastric motor index decreased by 27%. After considering the results of the current investigation, it can be stated that NO system imbalance leads to desynchronization of gastric active phases and, perhaps, reassigns the influence of different compensatory-adaptive mechanisms. The longer is the L-NNA treatment, the more gastric functions are imbalanced and the stronger is the process of destruction.