Code, Charles F.

The rates of movement of chloride and water from ileal loops into blood (insorption) and from blood into ileal contents (exsorption) were determined in dogs by the use of radiochloride and deuterium. The transmural electrical potential was measured. The appropriate values then were applied to Ussing's equation. The data indicated that chloride is actively transported by the ileum of the dog. The addition of acetazolamide (Diamox) decreased the observed transport flux ratio of chloride to a value which was similar to the calculated value for passive transport. It was concluded that acetazolamide inhibited active transport of chloride. When acetazolamide was present, the insorption of chloride was decreased while the exsorption of chloride was not affected. Water transport was decreased in parallel with chloride transport. Determinations of carbon dioxide content of the luminal fluid during the tests suggested that the effect of acetazolamide on chloride and water insorption is not related to its carbonic anhydraseinhibiting action.

This study attempted to determine whether the slow basic electrical rhythms of the antrum and the duodenum were related, and to search for relationships between the fast electrical activities of the two regions. Observations were made on five healthy, trained, unanesthetized dogs by means of detecting electrodes surgically implanted on the walls of the antrum and duodenum. No relationship was found, in either fasted or fed dogs, between the slow electrical rhythms of the antrum and duodenum. Feeding increased the fast activity in the antrum and in the duodenum, and under these circumstances, the fast activity in the duodenum was related to the slow basic electrical rhythm of the antrum.

Recordings of pressure and electric potentials from Biebl loops of the duodenum of trained dogs were used to quantitate and to determine relationships among basic electric rhythm (BER), irregular bursts of spike potentials, and motor action of the duodenum. After control periods, morphine was used to stimulate rhythmic motor activity. The omnipresence of a stable, longitudinally propagated BER was demonstrated, each phase of which was detected simultaneously by electrodes arranged radially in the wall of the gut. Spike potentials were recorded whenever contraction of the gut wall was detected. The spikes occurred during a limited segment of the BER. Their number and amplitude were directly related to the strength of the contractions. Under control conditions, duodenal contractions associated with the spike potentials produced type I waves in the pressure record. Neither the spike potentials nor the type I contractions were conducted more than a few centimeters. With morphine only the latter portion of the BER showed minor changes. Incidence of spike potentials and contractions was increased. Occasionally morphine induced motor spasms, accompanied by a prolonged series of spike-like potentials and disruption of the BER.

This study was undertaken to define the motor activity of the fundus of the stomach. Observations were made on six healthy dogs with vagally innervated mucosal septal pouches of the fundus of the stomach and four other healthy dogs with identical pouches of the corpus of the stomach. In each dog the motor actions of the esophagus, gastroesophageal sphincter, gastric pouch, and gastric antrum were recorded simultaneously. The commonest motor activity recorded from the pouches of the fundus was a slow, phasic change in pressure or tone designated as a type III wave. Tiny pressure changes occurring at a rate of 5/min and identical to type I waves seen elsewhere in the stomach were sometimes recorded. Large "fundic" waves, occurring, when they were rhythmic, at a rate of about 3/min were occasionally seen on the records. Relaxation of the pouch of the fundus occurred after the majority of swallows, confirming the observation of other investigators that receptive relaxation of the fundus is an important component of the response to deglutition.

In preparation for a study of the electric activity in the wall of the gastroduodenal junction in unanesthetized trained dogs, the pyloric portion of the stomach (antrum), the pylorus, and the first portion of the duodenum were exteriorized surgically. When the animals were fully recovered, needle electrodes were inserted into the wall of the bowel for the detection of electric activity. The pylorus was found to act as an "electric insulator" between the stomach and the duodenum. The basic electric rhythm (BER) and the fast or spike activity detected in both the pyloric canal and the duodenal bulb became attenuated in the pylorus and usually disappeared in it. The BER of the antrum had a mean frequency of 4.4 cycle/min and spike potentials sometimes were associated with it. The frequency of the BER in the duodenal bulb was the same as in the duodenum but its voltage was less and its form more irregular. Spike potentials in the bulb occurred during a greater portion of the BER and had a greater tendency to distort the BER than in the more distal duodenum.

The rates of movement of isotopically labeled water, sodium and potassium from the contents of segments of duodenum and ileum into the blood (insorption) and from blood to the contents (exsorption) were determined in dogs. The insorption of labeled water and sodium from the duodenal and ileal segments was exponential in character. Calculation of insorption and exsorption using the exponential rate and the Visscher formulation gave similar values. Anesthesia produced by pentobarbital sodium had no effect on the insorption of water and sodium from the intestinal segments, but it caused a small decrease in exsorption into the duodenum. Acidification of the contents of the intestinal segments decreased insorption of water, sodium and potassium, whereas it increased the exsorption of sodium and potassium without altering that of water. The results indicate that the mucosa of the duodenum fulfills the function of equilibrating its contents by maintaining nearly equal and large movements of water and sodium in both directions, while that of the ileum is fixed to serve absorption (a net gain to the body) of water and sodium.

This study was undertaken to determine rates of insorption of radiosodium and radiopotassium from secreting and nonsecreting stomachs of rats. The methods employed have been described previously. Insorption of radiosodium from gastric contents to blood was always faster in nonsecreting than in acid-secreting stomachs. At the end of 15, 30, and 45 min the mean percentages insorbed from stomachs secreting acid were 1.6, 3.1, and 4.5, whereas from stomach not secreting acid the mean percentages were 5.8, 9.3 and 11.7, respectively. In contrast, the rate of insorption of radiopotassium was unaffected by presence or absence of acid. Its rate of insorption was uniformly low and about equal to the rate of insorption of radiosodium from the secreting stomach. The results demonstrate that the rat's stomach, like that of man and dog, offers a barrier to insorption of sodium which is more pronounced when acid is being secreted and that insorption of potassium, though slow, is unaffected by acid and most likely is independent of insorption of sodium.

Previous studies have shown that large exchanges of water and sodium occur in both directions across the mucosa of the duodenum between the contents and the blood as if to develop and maintain equilibrium with the plasma. In contrast, in the ileum the exchanges are directed to absorption of the contents rather than equilibration. These findings indicate differences in function of the mucosa of the two sites. To illuminate these, isosmotic and hypertonic solutions of a slowly absorbed substance (mannitol) were placed in duodenal and ileal segments of the small bowels of dogs. The changes in the composition of these solutions and the bidirectional fluxes of sodium and water have been determined. Although mannitol was absorbed by the two sites at equal rates and the osmolality of the contents of both regions changed in a parallel fashion, the composition of the contents in the two sites underwent quite different alterations. In the duodenum the volume was unchanged if the solution was isosmotic and increased if it was initially hypertonic, while in the ileum it decreased in both instances. Sodium always entered the duodenal contents in large quantities, while little appeared in the ileal contents.

The effect of increased portal pressure on the ileal sorption of sodium and water was determined in acute studies on anesthetized dogs. Portal pressure was controlled by an inflatable cuff placed around the vein and the movement of sodium and water into and out of a segment of the ileum was determined by use of Na22 and D2O. With the cuff in place but not inflated, exsorption of sodium (movement from blood to intestine) increased, but insorption of sodium (movement from intestine to blood) decreased, and the movement of water was little affected. Further increases in portal pressure produced a progressive increase in the rate of exsorption of sodium without having further significant effects on the insorption of sodium or the movement of water.

The pressure in the esophagus and its sphincters in seven well-trained, intact, healthy dogs was studied using three small water-filled polyethylene tubes attached to pressure transducers. To obtain resting pressures these tubes were withdrawn at intervals of 0.5–2.0 cm through the gastroesophageal junction, the esophagus and the pharyngoesophageal junction. Swallowing was induced by injection of water into the mouth or pharynx of the animals, and responses were recorded from selected sites. At rest, bands of elevated pressure about 2 cm wide were detected at the pharyngoesophageal and gastroesophageal junctions. The mean maximal pressures in the two zones were 20 and 6.9 cm of water, respectively. Pressure in the esophagus at rest was less than that in the gastric fundus. When swallowing began, the elevated pressure in the junctional zones decreased promptly, rose to high values as the peristaltic wave of deglutition swept into them, and then declined to resting levels. A peristaltic wave of high pressure swept through the esophagus with each swallow. These findings indicate that the junctional zones act as sphincters. Their behavior is identical to that in healthy human beings. The pressure pattern in the esophagus itself with swallowing is also the same in the two species, but in the dog the peristaltic wave moves faster and the rise of pressure is briefer. These differences may reflect the fact that the muscle of the dog's esophagus is entirely skeletal.