Search

The myoelectrical and mechanical activities of the totally isolated, canine stomachs were recorded using five sets of bipolar silver-wire electrodes and one strain gauge. Stomachs were perfused extracorporeally with the blood of living supporting dogs which served as oxygenators and dialysers. Each supporting dog had a permanent antral pouch, accessible for the purpose of irrigation. To suppress the release of endogenous gastrin, this antral pouch and the antrum of the ex vivo stomach were irrigated with acid (pH 3). To induce the release of gastrin, one or both antra were irrigated with 0.2-percent acetylcholine or with 1 M glycine. To compare the action of endogenous gastrin with exogenous gastrin-like peptide, pentagastrin was infused into the gastric artery in doses of 4 mug/h and 8 mug/h. Control recordings were done during the acid irrigation. Endogenous gastrin released from antra by acetylcholine or glycine caused identical changes in the recordings as exogenous pentagastrin. There was a marked increase in the frequency of electrical control activity and of gastric contractions recorded as increased mechanical response. The results indicate that the ex vivo stomach can be used for study of the effect of endogenous gastrin musculature activity under the experimental conditions described.

Electrical and mechanical activity was recorded from totally isoltted porcine stomachs perfused with homologous blood, The electrical control activity, response activity, and mechanical reaction to various hormones and drugs stimulationg these activities were recorded. The drugs were injected directly into the gastric artery of the isolated organ. Normal response to cholinergic stimulants and to pentagastrin was observed. The effect of blockers such as atropine, hexamethonium and tetrodotosin on the action of stimulants was also assessed. The results of this study suggest that the release of acetylcholine is involved in the mechanism of action of pentagastrin. They also demonstrate the usefulness of the isolated porcine stomach approach to the study of gastric myoelectrical and mechanical activity.

Electrical and mechanical activity was recorded from six totally isolated canine stomachs perfused with homologous blood oxygenated in vitro. Reactions to electrical vagal stimulation to cholinergic drugs and to pentagastrin were recorded. Electrical control activity, electrical response activity and mechanical response of isolated stomachs, observed in this in vitro system, were identical to those found in canine-isolated stomachs perfused with cross-circulated blood of living animals. It appears that when a living animal is included in the perfusion system of the isolated stomach, drugs used for gastric stimulation are rapidly metabolized and, due to this physiological clearance, repeated injections of stimulants can be given for several hours. Using the in vitro perfusion system, as in this experiment, injected drugs accumulate in the perfusion blood, as no clearance mechanism is available. Partial or total exchange of perfusion blood is therefore recommended. With these reservations, the in vitro system appears to be an easy method for the study of nonstimulated and stimulated electrical and mechanical activity of the totally isolated canine stomach.

Electrical and mechanical activity were recorded from totally isolated whole porcine stomachs perfused with homologous blood. Stagnant, complete ischemia was then produced by closing the gastric artery and vein for various periods of time up to 3 h. After a given period of ischemia, blood was recirculated for 10 min and then pentagastrin was injected into the gastric artery. The vagus nerve was also electrically stimulated at various stages of anoxia and recirculation. After up to 90 min of ischemia, stomachs were able to demonstrate electrical control activity of low frequency after 10 min of blood recirculation. After injection of pentagastrin, electrical control activity rapidly became normal. When ischemia lasted 120 min or longer, recirculation of blood did not induce reappearance of electrical control activity, but pentagastrin injection produced a normal response. After ischemia of 240 min duration or longer, recirculation and pentagastrin had no effect. In previously ischemic stomachs the response to vagal stimulation occurred only in the stomachs responding to pentagastrin.

Electrical and mechanical activities were recorded from the totally isolated canine stomach perfused with homologous blood of a living oxygenator-supported dog. Stagnant ischemic anoxia was induced by closing inflow and outflow blood from the isolated organ for various periods of time up to four hours. Recording of electrical and mechanical activity was performed prior to, during, and after the anoxic periods. After a given period of ischemia, blood was recirculated for ten minutes, and the pentagastrin was injected into the gastric artery. After up to three hours of anoxia, stomachs were able to show recordable electrical activity when perfused for ten minutes with homologous blood. Up to this period of three hours, stomachs also responded to the injection of pentagastrin. Pentagastrin accelerated the normalization of electrical and mechanical activity of previously anoxic stomachs. After 3.5 to 4.0 hours of anoxia, recirculation of blood through the stomach and injection of pentagastrin had no effect on electrical and mechanical activity of the gastric musculature.